J. Nol.
Biol. (1977) 113, 443-447
LETTERS TO THE EDITOR
Crystallographic
Study of Plastocyanins
C’ryst,als of plastocyanins from pea and corn lea\-es ha\Te been obt,ained. Rot11 are suitable for X-ray structure analysis with a resolution up to 1.8 8. The crystal form of plastocyanin from pea leaves belorlgs to the space group P2I2,21 wit,h unit ~11 dimensions: a = 4!).0 A, b = 53.3 A, c = 82.6 B. The assumed member of prot,ein molecules per asymmetric unit of the unit cell is two. Crystals of the oxidized (CuZf ) and reduced (Cu’ ) forms are isomorphic. No essential differences in spot intensities for the main zone’ with a resolution of 3 A were rcxvealed. The crystal form of plastocyanin from corn leaves belongs to the space group 1’1 with unit cell parameters: a = 24.8 A, b = 30.0 A, c = 58.5 Ai and a := M”10’. /? = 87”08’, y :. 78”40’. The nssumcvI nllmhcr of prokin molecules pvr asymnwtric unit is two. Plnstocynnin is one of the main proteins of the electron t,ransport chain in photosynthetic systems. This protein has been found in many photosynthetic organisms including higher plants and bacteria. Plastocyanins usually have a molecular weight, of about 10,500 and conta’in one copper atom. In some cases, however, for example in spinach plastocyanin, a quaternary structure seems to be observed with a total molecular weight of about’ 40,000 (Siegelman et al., 1976). In this letter we present data from a crystallographic study of plastocyanins from pea and corn leaves. Plastocyanin from pea leaves (Pisum satiwum L.) was isolated using the procedure described by Garber et al. (1976). Plastocyanin from corn leaves (Zea may) was kindly presented by Dr N. F. PJesnayko (Institute of Photosynthesis, Poustchino). Both preparations were purified by gel filtration on Sephadex G75 and by chromatograph> on DEAF,-cellulose. The proteins were homogeneous according to data obtained from gel electrophoresis. In the oxidized form they had an absorption spectrum typical for plastocyanins, the absorption ratio A,7,/A5S7 was in the range of 1.1 t’o 1.3. Crystallization of the pea plastocyanin was done in a 1 to 29/o solution of the oxidized protein (deep blue) in a 0.05 M-phosphate buffer (pH 7.0) with 0.1 mM-CuSO, at about ~-4”c). Ammonium sulphate as a precipitant was introduced gradually int’o the protein solution by dialysis. At 67 y0 saturation with ammonium sulphate needle-like microcrystals a few micromet’res long usually appeared. Sometimes under the same conditions rod-like microcrystals with a rectangular cross-section also appeared. The lat,ter were used as seeds to grow large monocrystals. Seeds were introduced int’o a 1)
Biol. (1977) 113, 443-447
LETTERS TO THE EDITOR
Crystallographic
Study of Plastocyanins
C’ryst,als of plastocyanins from pea and corn lea\-es ha\Te been obt,ained. Rot11 are suitable for X-ray structure analysis with a resolution up to 1.8 8. The crystal form of plastocyanin from pea leaves belorlgs to the space group P2I2,21 wit,h unit ~11 dimensions: a = 4!).0 A, b = 53.3 A, c = 82.6 B. The assumed member of prot,ein molecules per asymmetric unit of the unit cell is two. Crystals of the oxidized (CuZf ) and reduced (Cu’ ) forms are isomorphic. No essential differences in spot intensities for the main zone’ with a resolution of 3 A were rcxvealed. The crystal form of plastocyanin from corn leaves belongs to the space group 1’1 with unit cell parameters: a = 24.8 A, b = 30.0 A, c = 58.5 Ai and a := M”10’. /? = 87”08’, y :. 78”40’. The nssumcvI nllmhcr of prokin molecules pvr asymnwtric unit is two. Plnstocynnin is one of the main proteins of the electron t,ransport chain in photosynthetic systems. This protein has been found in many photosynthetic organisms including higher plants and bacteria. Plastocyanins usually have a molecular weight, of about 10,500 and conta’in one copper atom. In some cases, however, for example in spinach plastocyanin, a quaternary structure seems to be observed with a total molecular weight of about’ 40,000 (Siegelman et al., 1976). In this letter we present data from a crystallographic study of plastocyanins from pea and corn leaves. Plastocyanin from pea leaves (Pisum satiwum L.) was isolated using the procedure described by Garber et al. (1976). Plastocyanin from corn leaves (Zea may) was kindly presented by Dr N. F. PJesnayko (Institute of Photosynthesis, Poustchino). Both preparations were purified by gel filtration on Sephadex G75 and by chromatograph> on DEAF,-cellulose. The proteins were homogeneous according to data obtained from gel electrophoresis. In the oxidized form they had an absorption spectrum typical for plastocyanins, the absorption ratio A,7,/A5S7 was in the range of 1.1 t’o 1.3. Crystallization of the pea plastocyanin was done in a 1 to 29/o solution of the oxidized protein (deep blue) in a 0.05 M-phosphate buffer (pH 7.0) with 0.1 mM-CuSO, at about ~-4”c). Ammonium sulphate as a precipitant was introduced gradually int’o the protein solution by dialysis. At 67 y0 saturation with ammonium sulphate needle-like microcrystals a few micromet’res long usually appeared. Sometimes under the same conditions rod-like microcrystals with a rectangular cross-section also appeared. The lat,ter were used as seeds to grow large monocrystals. Seeds were introduced int’o a 1)
