Inactivation of the Alamethicin-Induced Conductance Caused by Quaternary Ammonium Ions and Local Anesthetics J A M E S J. D O N O V A N a n d R A M O N L A T O R R E From the Department of Physiology, Harvard Medical School, Boston, Massachusetts 02115
A B S T R AC T Long alkyl chain quaternary ammonium ions (QA), the local anesthetics (LA) tetracaine and lidocaine, imipramine, and pancuronium cause inactivation of the alamethicin-induced conductance in lipid bilayer membranes. The alamethicin-induced conductance undergoes inactivation only when these amphipathic compounds are added to the side containing alamethicin. The concentration of QA required to cause a given amount of inactivation depends on the length of the hydrocarbon chain and follows the sequence C9 > Ca0 > Ca2 > Can. LA and imipramine, in contrast to QA or pancuronium, are able to promote appreciable inactivation only if the pH of the alamethicin-free side is equal to or lower than the pK of these compounds. The membrane permeability to QA, LA, or imipramine is directly proportional to the alamethicin-induced conductance and is larger than the one for potassium. The observed steady state and time-course of the inactivation are well described by a model similar to that proposed by Heyer et al. (1976.J. Gen. Physiol. 67:703-729) and extended for any value of the diffuse double layer potential and for LA and imipramine. In this model QA, LA, or imipramine are able to permeate through the membrane only when the alamethicin-induced conductance is turned on. The amphipathic compounds then bind to the other membrane surface, changing the transmembrane potential and turning the conductance off. For a given concentration of QA, LA, or imipramine the extent of inactivation depends on two factors: first, the binding characteristics of these compounds to the membrane surface and second, their ability to permeate through the membrane when the alamethicin-induced conductance is turned on. The several possible mechanisms of permeation of the amphipathic molecules tested are discussed. INTRODUCTION
In excitable cells ionic permeability is regulated by the o p e n i n g a n d closing o f channels that are highly voltage sensitive. A p r o p e r t y that is c o m m o n to several v o l t a g e - d e p e n d e n t channels is inactivation. A p r i m e e x a m p l e o f inactivation is p r o v i d e d by the sodium channel in nerve ( H o d g k i n a n d Huxley, 1952; Bezanilla and A r m s t r o n g , 1977). In response to m e m b r a n e depolarization the m e m b r a n e sodium c o n d u c t a n c e reaches a peak and then decreases with a time constant o f milliseconds. A l t h o u g h the potassium c o n d u c t a n c e in nerve does not inactivate in the same time span as the sodium system does, it presents a long term inactivation u p o n p r o l o n g e d depolarization (Ehrenstein and Gilbert, 1966). J. G~N. P~vsloL. @ The Rockefeller University Press 90022-1295/79/04/0425127$1.00 Volume 73 April 1979 425--451
425
496
THE JOURNAL
OF
GENERAL
PHYSIOLOGY
9 VOLUME
73 9 1979
Moreover, Armstrong (1971, 1975) has found that when quaternary ammonium derivatives containing a long alkyl chain are present inside the axon, the timecourse of the potassium current changes drastically: it rises to a peak and then decreases to a low value. Thus, in the presence of these compounds potassium channels "inactivate." In artificial lipid bilayer membranes several substances have been shown to induce voltage-dependent conductances; among these, excitability-inducing material (Lecar et al., 1975; Ehrenstein et al., 1978), suzukacillin (Boheim et al., 1976) and monazomycin (Heyer et al., 1976 a) also show inactivation under the appropriate conditions. In particular, Heyer et al. (1976 b) have shown that the voltage-dependent conductance induced by monazomycin "inactivates" when quaternary ammonium ions having long alkyl chains are introuduced in the compartment containing monazomycin. This paper concerns the interaction of quaternary ammonium ions, local anesthetics, and other tertiary amines with the alamethicin channel. Alamethicin, isolated from the fungus Trichoderma viride, is a peptide consisting of 19 amino acids, with a high content of hydrophobic residues. The structure of alamethicin, once thought to be cyclic (Payne et al., 1970) has recently been reported to be linear (Martin and Williams, 1976). When present in micromolar amounts on one side of a lipid bilayer membrane, alamethicin is able to induce a strong voltage-dependent conductance (Mueller and Rudin, 1968) that can mimic in many aspects those found in excitable cells. The membrane conductance is an exponential function of voltage, increasing an e-fold every 4-6 mV (Eisenberg et al., 1973; Gordon and Haydon, 1975; Gisin et al., 1977). Alamethicin-induced steady-state conductance (Gs0 is also strongly dependent on both salt and polypeptide concentration and can be represented by (Eisenberg et al., 1973; Gordon and Haydon, 1975). G~ - C~alaC~~
(1)
where C ala and C salt are respectively the alamethicin and salt concentrations, e is the electronic charge, V,, is the transmembrane potential, and k and T have their usual meanings. The parameters a,/3, and y depend to a certain extent on membrane composition. For membranes made from phosphatidylethanolamine-decane (Eisenberg et al., 1973) or from glycerolmonooleate-hexadecane (Gordon and Haydon, 1975), the data can be described with ot = 9 +- 1,/3 = 4 +-- 1, and y = 6. There is strong evidence that alamethicin-induced conductance arises as a consequence of ion channel formation through the membrane. The main evidence supporting this conclusion comes from records of conductance fluctuations taken at low alamethicin concentrations. Conductance fluctuations appear in bursts and each burst has several conductance levels, which are nonintegral multiples of each other and which always appear in a sequential order (Gordon and Haydon, 1972; Eisenberg et al., 1973; Boheim, 1974). We present here evidence that alamethicin-induced conductance in lipid bilayers undergoes inactivation when quaternary ammonium ions, local anesthetics, or other pharmacologically important quaternary ammonium compounds and tertiary amines are present in the compartment containing alamethicin. The mechanism of this interaction can tell us a good deal about the
DONOVAN AND LATORRE Inactivationof Alamethicin-lnducedConductance
427
a r c h i t e c t u r e o f t h e a l a m e t h i c i n c h a n n e l a n d is r e l e v a n t to t h e u n d e r s t a n d i n g o f i n a c t i v a t i o n in b i o l o g i c a l m e m b r a n e s . T h e p r e s e n t d a t a i n d i c a t e s t h a t t h e i n a c t i v a t i o n is c a u s e d b y a c h a n g e in t h e t r a n s m e m b r a n e p o t e n t i a l p r o m o t e d by a f l u x o f t h e i n a c t i v a t i n g c o m p o u n d t h r o u g h t h e m e m b r a n e , a n d t h a t this f l u x is d i r e c t l y a s s o c i a t e d w i t h t h e o p e n i n g o f t h e a l a m e t h i c i n c h a n n e l s . MATERIALS
AND M E T H O D S
Membrane Formation Except in the case where asymmetric membranes were used (see below) all membranes were f o r m e d from a mixture o f glyceroimonooleate (GMO) and phosphatidylserine (PS) in a ratio o f G M O : P S of 2:1 (wt/wt). This lipid mixture combines the advantages of having a negative surface potential, and having fairly fast alamethicin kinetics. Lipids were stored at -50~ in CHCI3 solutions. A portion o f this solution was evaporated with a stream o f nitrogen, and redissolved in pentane at a concentration of 12.5 mg/ml. Pentane solutions were p r e p a r e d fresh every day. Membranes were f o r m e d by the method o f Montal and Mueller (1972). Two chambers each with a 3-ml capacity were separated by a thin (12-/~m) Teflon partition (Fluorofilm, Dielectrix Corp., Farmingdale, N.Y.) in which a small hole (4.5 • 10-4 cm 2 area) was punched. T h e hole was p u n c h e d by using a hypodermic needle (27 gauge) which was filed down to have a flat tip and then sharpened as a bore. T h e hole in the partition was treated with a 5% solution of squalene in pentane. T h e pools o f the chamber had a surface area o f 4 cm 2. Monolayers were spread on the surface o f the electrolyte solution with 10/xl of the a p p r o p r i a t e lipid solution. Membranes were formed by adding solution simultaneously to both compartments, and by raising the liquid until the hole was completely covered. As indicated by their high specific capacitance (0.75 /zF/cm 2) and their low compressibility, m e m b r a n e s formed by pretreating the hole with squalene are effectively "solvent-free" (see also White, 1978). Membrane conductance was usually - 1 ms the normal time-course can be adequately described by a single exponential (see Fig. 3) described by I ( t ) = 1(oo)[1 - e x p ( - t / r ) ] ,
where r = 25 ms. Bringing in the inactivation factors, the net time-course of the c u r r e n t is I (t) = I (oo)[1 - exp ( - t/~-)]exp [ - 4.4 Ws(t)/25],
(fib)
which has an ascending phase and a descending phase. Again, the AW~(t) is determined by C~ ([C+] t) with Eq. 8 a. Because A ~ ( t ) increases nonlinearly with time, the expected time-course of inactivation is not described by a single exponential. We thank Dr. J. Z. Yeh for suggesting the experiment with pancuronium. This study was supported by grant GM-27715 from the National Institutes of Health. Mr. Donovan was supported by a predoctoral fellowship from the National Science Foundation. Received for publication 18 August 1978.
450
THE JOURNAL OF GENERAL PHYSIOLOGY " VOLUME 73 " 1979 REFERENCES
ALVAREZ, O., and R. LATORRE. 1978. Voltage-dependent capacitance in lipid bilayers made from monolayers. Biophys. J. 21:1-17. ARMSTRONG, C, M. 1971. Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons.J. Gen. Physiol. 58:413-437. ARMSTRONG,C. M. 1975. Ionic pores, gates, and gating currents. Q. Rev. Biophys. 7:179210. AVEYARD, R., and D. A. HAYDON. 1973. An Introduction to the Principles of Surface Chemistry. Cambridge University Press, London. 232 pp. BAMBERG, E., and K. JANKO. 1976. Single channel conductance in lipid bilayer membranes in presence of monazomycin. Biochim. Biophys. Acta. 426:447-450. BAUMANN, G., and P. MODELER. 1974. A molecular model of membrane excitability. J. Supramol. Struct. 2:538-557. BEZAmLLA, F., and C. M. ARMSTRONG. 1977. Inactivation of the sodium channel. I. Sodium current experiments.J. Gen Physiol. 70:549-566. BLAre, E. J., and C. A. KRAUS. 1951. Properties of electrolytic solutions. XLVIII. Conductance of some long chain salts in water at +25 ~ J. Am. Chem. Soc. 75:1129-1150. BonzlM, G. 1974. Statistical analysis of alamethicin channels in black lipid membranes.J. Membr. Biol. 19:277-303. BOHEIM, G., K. JANKO, D. LEIBFRITZ, T. OOKA, W . A. KONIG, and G. JUNG. 1976. Structural and membrane modifying properties of suzukacillin, a peptide antibiotic related to alamethicin. Part B. Pore formation in black lipid films. Biochim. Biophys. Acta. 455:182-199. BOHEIM, G., and H. A. KOLn. 1978. Analysis of the multi-pore system of alamethicin in a lipid membrane. I. Voltage-jump current-relaxation measurements.J. Membr. Biol. $8:99-150. EHRENSTEXN, G., and D. L. GILBERT. 1966. Slow changes of potassium permeability in the squid giant axons. Biophys. J. 6:553-566. EHRENSTEIN, G., H. LECAR, and R. LATORRE. 1978. Inactivation in bilayer and natural excitable membranes. In Membrane Transport Processes. Vol. 2. D. C. Tosteson, Y. V. Ovchinnikov, and R. Latorre, editors. Raven Press, New York. EISENBERG, M. 1972. Voltage gateable ionic pores induced by alamethicin in black lipid membranes. Ph.D. thesis. Calif. Inst. Tech., Pasadena, Calif. EISZNBERG, M., J. E. HALL, and C. A. MEAl). 1973. The nature of the voltage-dependent conductance induced by alamethicin in black lipid membranes.J. Membr. Biol. 14:143176. GISlN, B. F., S. KOBAYASHI,and J. E. HALL. 1977. Synthesis of a 19-residue peptide with alamethicin-like activity. Proc. Natl. Acad. Sci. U.S.A. 74:115-119. GORDON, L. G. M., and D. A. HAYDON. 1972. The unit conductance channel of alamethicin. B iochim. B iophys . A cta 255:1014-1018. GORDON, L. G. M., and D. A. HAYDON. 1975. Potential-dependent conductances in lipid membranes containing alamethicin. Philos. Tram. R. Soc. Lond. B Biol. Sci. 270:433447. GORDON, L. G. M., and D. A. HAYDON. 1976. Kinetics and stability of alamethicin conducting channels in lipid bilayers. Biochim. Biophys. Acta. 436:541-546. HArt)ON, D. A., and V. B. MYERS. 1973. Surface charge, surface dipoles and membrane conductance. Biochim. Biophys. Acta. 307:429-443.
DONOVANAND LATORRE Inactivation of Alamethicin-Induced Conductance
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HAYDON, D. A., and J. H. PmLLIPS. 1958. The Gibbs equation for soluble ionized monolayers in absence of added electrolyte at the oil-water interface. Tram. Faraday Soc. 59:698-706. HEvra, E. J., R. U. MUI~LEa,and A. FINKELSTr1N.1976 a. Inactivation of monazomycininduced voltage-dependent conductance in thin lipid membranes. II. Inactivation produced by monazomycin transport through the membrane.J. Gen. Physiol. 67:731748. HEVEa, E. J., R. U. MULLER,and A. FINKELSTrIN.1976 b. Inactivation of monazomycininduced voltage-dependent conductance in thin lipid films. I. Inactivation by long chain quaternary ammonium ions.J. Gen. Physiol. 67:703-729. Hn~LE, B. 1977. The pH-dependent rate of action of local anesthetics on node of Ranvier.J. Gen. Physiol. 69:475-496. HLADKY, S. B., and D. A. HAYDON. 1973. Membrane conductance and surface potential. Biochim. Biophys. Acta. 318:464-469. HODCKIN, A. L., and A. F. HUXLEY. 1952. A quantitative description of membrane current and its application to conductance and excitation of nerve.J. Physiol. (Loncl.). 117:500-544. LECAR, H., G. EHERENSTEIN,and R. LATORItE. 1975. Mechanism for channel gating in excitable bilayers. Ann. N.Y. Acad. Sci. 264:303-313. MAaTIN, D. R., and R. J. P. WILLIAMS. 1976. Chemical nature and sequence of alamethicin. Biochem. J. 153:181-190. McLAuo~LIN, S. 1977. Electrostatic potentials at membrane-solution interfaces. Curr. Top. Membranes Tramp. 9:71-144. McLAuGHLIN, S. G. A., G. SZABO, G. EISENMAN,and S. M. CmNI. 1970. Surface charge and the conductance of phospholipid membranes. Proc. Natl. Acad. Sci. U.S.A. 67: 1268-1275. MONTAL, M., and P. MtJELLER. 1972. Formation of bimolecular membranes from lipid monolayers and a study of their electrical properties. Proc. Natl. Acad. Sci. U.S.A. 69: 3561-3566. MUELLrR, P., and D. O. RUDIN. 1968. Action potentials induced in bimolecular lipid membranes. Nature (Lond.) . 217:713. MULLrR, R. V., and A. FINKELSTEIN.1972. The effect of surface charge on the voltagedependent conductance induced in thin lipid membranes by monazomycin. J. Gen. Physiol. 60:285-306. PAVNE,J. W., R. JA~ES, and B. S. HARTLEV.1970. The primary structure of alamethicin. Biochem. J. 117:757-766. Pm~ssiAN, B. C. 1968. Ionophoric antibiotics as models for biological transport. Fed. Proc. 27:1283-1298. TANrOaD, C. 1973. The Hydrophobic Effect. John Wiley & Sons, Inc., New York. TANrORD, C. 1978. The hydrophobic effect and the organization of living matter. Science (Wash. D.C.). 200:1012-1018. WroTE, S. H. 1978. Formation of "solvent-free" black lipid membranes from glyceryl monooleate dispersed in squalene. Biophys. J. 25:337-347. YE~, J. z., and T. NAI~AHASm.1977. Kinetic analysis of pancuronium interaction with channels in squid axon membranes.J. Gen. Physiol. 69:293-323.
A B S T R AC T Long alkyl chain quaternary ammonium ions (QA), the local anesthetics (LA) tetracaine and lidocaine, imipramine, and pancuronium cause inactivation of the alamethicin-induced conductance in lipid bilayer membranes. The alamethicin-induced conductance undergoes inactivation only when these amphipathic compounds are added to the side containing alamethicin. The concentration of QA required to cause a given amount of inactivation depends on the length of the hydrocarbon chain and follows the sequence C9 > Ca0 > Ca2 > Can. LA and imipramine, in contrast to QA or pancuronium, are able to promote appreciable inactivation only if the pH of the alamethicin-free side is equal to or lower than the pK of these compounds. The membrane permeability to QA, LA, or imipramine is directly proportional to the alamethicin-induced conductance and is larger than the one for potassium. The observed steady state and time-course of the inactivation are well described by a model similar to that proposed by Heyer et al. (1976.J. Gen. Physiol. 67:703-729) and extended for any value of the diffuse double layer potential and for LA and imipramine. In this model QA, LA, or imipramine are able to permeate through the membrane only when the alamethicin-induced conductance is turned on. The amphipathic compounds then bind to the other membrane surface, changing the transmembrane potential and turning the conductance off. For a given concentration of QA, LA, or imipramine the extent of inactivation depends on two factors: first, the binding characteristics of these compounds to the membrane surface and second, their ability to permeate through the membrane when the alamethicin-induced conductance is turned on. The several possible mechanisms of permeation of the amphipathic molecules tested are discussed. INTRODUCTION
In excitable cells ionic permeability is regulated by the o p e n i n g a n d closing o f channels that are highly voltage sensitive. A p r o p e r t y that is c o m m o n to several v o l t a g e - d e p e n d e n t channels is inactivation. A p r i m e e x a m p l e o f inactivation is p r o v i d e d by the sodium channel in nerve ( H o d g k i n a n d Huxley, 1952; Bezanilla and A r m s t r o n g , 1977). In response to m e m b r a n e depolarization the m e m b r a n e sodium c o n d u c t a n c e reaches a peak and then decreases with a time constant o f milliseconds. A l t h o u g h the potassium c o n d u c t a n c e in nerve does not inactivate in the same time span as the sodium system does, it presents a long term inactivation u p o n p r o l o n g e d depolarization (Ehrenstein and Gilbert, 1966). J. G~N. P~vsloL. @ The Rockefeller University Press 90022-1295/79/04/0425127$1.00 Volume 73 April 1979 425--451
425
496
THE JOURNAL
OF
GENERAL
PHYSIOLOGY
9 VOLUME
73 9 1979
Moreover, Armstrong (1971, 1975) has found that when quaternary ammonium derivatives containing a long alkyl chain are present inside the axon, the timecourse of the potassium current changes drastically: it rises to a peak and then decreases to a low value. Thus, in the presence of these compounds potassium channels "inactivate." In artificial lipid bilayer membranes several substances have been shown to induce voltage-dependent conductances; among these, excitability-inducing material (Lecar et al., 1975; Ehrenstein et al., 1978), suzukacillin (Boheim et al., 1976) and monazomycin (Heyer et al., 1976 a) also show inactivation under the appropriate conditions. In particular, Heyer et al. (1976 b) have shown that the voltage-dependent conductance induced by monazomycin "inactivates" when quaternary ammonium ions having long alkyl chains are introuduced in the compartment containing monazomycin. This paper concerns the interaction of quaternary ammonium ions, local anesthetics, and other tertiary amines with the alamethicin channel. Alamethicin, isolated from the fungus Trichoderma viride, is a peptide consisting of 19 amino acids, with a high content of hydrophobic residues. The structure of alamethicin, once thought to be cyclic (Payne et al., 1970) has recently been reported to be linear (Martin and Williams, 1976). When present in micromolar amounts on one side of a lipid bilayer membrane, alamethicin is able to induce a strong voltage-dependent conductance (Mueller and Rudin, 1968) that can mimic in many aspects those found in excitable cells. The membrane conductance is an exponential function of voltage, increasing an e-fold every 4-6 mV (Eisenberg et al., 1973; Gordon and Haydon, 1975; Gisin et al., 1977). Alamethicin-induced steady-state conductance (Gs0 is also strongly dependent on both salt and polypeptide concentration and can be represented by (Eisenberg et al., 1973; Gordon and Haydon, 1975). G~ - C~alaC~~
(1)
where C ala and C salt are respectively the alamethicin and salt concentrations, e is the electronic charge, V,, is the transmembrane potential, and k and T have their usual meanings. The parameters a,/3, and y depend to a certain extent on membrane composition. For membranes made from phosphatidylethanolamine-decane (Eisenberg et al., 1973) or from glycerolmonooleate-hexadecane (Gordon and Haydon, 1975), the data can be described with ot = 9 +- 1,/3 = 4 +-- 1, and y = 6. There is strong evidence that alamethicin-induced conductance arises as a consequence of ion channel formation through the membrane. The main evidence supporting this conclusion comes from records of conductance fluctuations taken at low alamethicin concentrations. Conductance fluctuations appear in bursts and each burst has several conductance levels, which are nonintegral multiples of each other and which always appear in a sequential order (Gordon and Haydon, 1972; Eisenberg et al., 1973; Boheim, 1974). We present here evidence that alamethicin-induced conductance in lipid bilayers undergoes inactivation when quaternary ammonium ions, local anesthetics, or other pharmacologically important quaternary ammonium compounds and tertiary amines are present in the compartment containing alamethicin. The mechanism of this interaction can tell us a good deal about the
DONOVAN AND LATORRE Inactivationof Alamethicin-lnducedConductance
427
a r c h i t e c t u r e o f t h e a l a m e t h i c i n c h a n n e l a n d is r e l e v a n t to t h e u n d e r s t a n d i n g o f i n a c t i v a t i o n in b i o l o g i c a l m e m b r a n e s . T h e p r e s e n t d a t a i n d i c a t e s t h a t t h e i n a c t i v a t i o n is c a u s e d b y a c h a n g e in t h e t r a n s m e m b r a n e p o t e n t i a l p r o m o t e d by a f l u x o f t h e i n a c t i v a t i n g c o m p o u n d t h r o u g h t h e m e m b r a n e , a n d t h a t this f l u x is d i r e c t l y a s s o c i a t e d w i t h t h e o p e n i n g o f t h e a l a m e t h i c i n c h a n n e l s . MATERIALS
AND M E T H O D S
Membrane Formation Except in the case where asymmetric membranes were used (see below) all membranes were f o r m e d from a mixture o f glyceroimonooleate (GMO) and phosphatidylserine (PS) in a ratio o f G M O : P S of 2:1 (wt/wt). This lipid mixture combines the advantages of having a negative surface potential, and having fairly fast alamethicin kinetics. Lipids were stored at -50~ in CHCI3 solutions. A portion o f this solution was evaporated with a stream o f nitrogen, and redissolved in pentane at a concentration of 12.5 mg/ml. Pentane solutions were p r e p a r e d fresh every day. Membranes were f o r m e d by the method o f Montal and Mueller (1972). Two chambers each with a 3-ml capacity were separated by a thin (12-/~m) Teflon partition (Fluorofilm, Dielectrix Corp., Farmingdale, N.Y.) in which a small hole (4.5 • 10-4 cm 2 area) was punched. T h e hole was p u n c h e d by using a hypodermic needle (27 gauge) which was filed down to have a flat tip and then sharpened as a bore. T h e hole in the partition was treated with a 5% solution of squalene in pentane. T h e pools o f the chamber had a surface area o f 4 cm 2. Monolayers were spread on the surface o f the electrolyte solution with 10/xl of the a p p r o p r i a t e lipid solution. Membranes were formed by adding solution simultaneously to both compartments, and by raising the liquid until the hole was completely covered. As indicated by their high specific capacitance (0.75 /zF/cm 2) and their low compressibility, m e m b r a n e s formed by pretreating the hole with squalene are effectively "solvent-free" (see also White, 1978). Membrane conductance was usually - 1 ms the normal time-course can be adequately described by a single exponential (see Fig. 3) described by I ( t ) = 1(oo)[1 - e x p ( - t / r ) ] ,
where r = 25 ms. Bringing in the inactivation factors, the net time-course of the c u r r e n t is I (t) = I (oo)[1 - exp ( - t/~-)]exp [ - 4.4 Ws(t)/25],
(fib)
which has an ascending phase and a descending phase. Again, the AW~(t) is determined by C~ ([C+] t) with Eq. 8 a. Because A ~ ( t ) increases nonlinearly with time, the expected time-course of inactivation is not described by a single exponential. We thank Dr. J. Z. Yeh for suggesting the experiment with pancuronium. This study was supported by grant GM-27715 from the National Institutes of Health. Mr. Donovan was supported by a predoctoral fellowship from the National Science Foundation. Received for publication 18 August 1978.
450
THE JOURNAL OF GENERAL PHYSIOLOGY " VOLUME 73 " 1979 REFERENCES
ALVAREZ, O., and R. LATORRE. 1978. Voltage-dependent capacitance in lipid bilayers made from monolayers. Biophys. J. 21:1-17. ARMSTRONG, C, M. 1971. Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons.J. Gen. Physiol. 58:413-437. ARMSTRONG,C. M. 1975. Ionic pores, gates, and gating currents. Q. Rev. Biophys. 7:179210. AVEYARD, R., and D. A. HAYDON. 1973. An Introduction to the Principles of Surface Chemistry. Cambridge University Press, London. 232 pp. BAMBERG, E., and K. JANKO. 1976. Single channel conductance in lipid bilayer membranes in presence of monazomycin. Biochim. Biophys. Acta. 426:447-450. BAUMANN, G., and P. MODELER. 1974. A molecular model of membrane excitability. J. Supramol. Struct. 2:538-557. BEZAmLLA, F., and C. M. ARMSTRONG. 1977. Inactivation of the sodium channel. I. Sodium current experiments.J. Gen Physiol. 70:549-566. BLAre, E. J., and C. A. KRAUS. 1951. Properties of electrolytic solutions. XLVIII. Conductance of some long chain salts in water at +25 ~ J. Am. Chem. Soc. 75:1129-1150. BonzlM, G. 1974. Statistical analysis of alamethicin channels in black lipid membranes.J. Membr. Biol. 19:277-303. BOHEIM, G., K. JANKO, D. LEIBFRITZ, T. OOKA, W . A. KONIG, and G. JUNG. 1976. Structural and membrane modifying properties of suzukacillin, a peptide antibiotic related to alamethicin. Part B. Pore formation in black lipid films. Biochim. Biophys. Acta. 455:182-199. BOHEIM, G., and H. A. KOLn. 1978. Analysis of the multi-pore system of alamethicin in a lipid membrane. I. Voltage-jump current-relaxation measurements.J. Membr. Biol. $8:99-150. EHRENSTEXN, G., and D. L. GILBERT. 1966. Slow changes of potassium permeability in the squid giant axons. Biophys. J. 6:553-566. EHRENSTEIN, G., H. LECAR, and R. LATORRE. 1978. Inactivation in bilayer and natural excitable membranes. In Membrane Transport Processes. Vol. 2. D. C. Tosteson, Y. V. Ovchinnikov, and R. Latorre, editors. Raven Press, New York. EISENBERG, M. 1972. Voltage gateable ionic pores induced by alamethicin in black lipid membranes. Ph.D. thesis. Calif. Inst. Tech., Pasadena, Calif. EISZNBERG, M., J. E. HALL, and C. A. MEAl). 1973. The nature of the voltage-dependent conductance induced by alamethicin in black lipid membranes.J. Membr. Biol. 14:143176. GISlN, B. F., S. KOBAYASHI,and J. E. HALL. 1977. Synthesis of a 19-residue peptide with alamethicin-like activity. Proc. Natl. Acad. Sci. U.S.A. 74:115-119. GORDON, L. G. M., and D. A. HAYDON. 1972. The unit conductance channel of alamethicin. B iochim. B iophys . A cta 255:1014-1018. GORDON, L. G. M., and D. A. HAYDON. 1975. Potential-dependent conductances in lipid membranes containing alamethicin. Philos. Tram. R. Soc. Lond. B Biol. Sci. 270:433447. GORDON, L. G. M., and D. A. HAYDON. 1976. Kinetics and stability of alamethicin conducting channels in lipid bilayers. Biochim. Biophys. Acta. 436:541-546. HArt)ON, D. A., and V. B. MYERS. 1973. Surface charge, surface dipoles and membrane conductance. Biochim. Biophys. Acta. 307:429-443.
DONOVANAND LATORRE Inactivation of Alamethicin-Induced Conductance
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