l. 1990 Oxford University Press

Nucleotide

Nucleic Acids Research, Vol. 18, No. 20 6129

sequence

of guinea-pig x-casein cDNA

Len Hall Department of Biochemistry, University of Bristol, Bristol BS8 ITD, UK EMBL accession

Submitted September 19, 1990

Caseins are the major secretory proteins synthesised in the lactating mammary gland. These phosphoproteins are present in the milk as stable aggregates called micelles, the structure of which is stabilised against precipitation by the x-casein. Guinea-pig a%1, a%2 and casein cDNAs have been cloned (1) and the sequences of the two species are available (2,3). During these studies a cDNA clone designated pgpO5 was partially characterised (4) and found to correspond to a 1.25 kb RNA transcript. DNA sequence analysis has now revealed that this cDNA clone encodes guinea-pig x-casein. The deduced amino acid sequence (Mr 25,582) shows a high degree of similarity to x-caseins from other species (5). Features to note include: (i) a 21-residue signal peptide, one of the most highly conserved regions of the xcaseins; (ii) the conserved chymosin sensitive bond (Phe 97a

86

167

248

CCT TTT TTG GCT GCA P F L A A -1 GTC CTG TAT CTA TTA V L Y L L

CCA ATT MT AAC P I N N 50

GAG E +1 AGC S

REFERENCES 1. 2. 3. 4. 5.

CCG GTC TCG ACA P V S T

410

AAA ATT CTA GGA AAA GCC

80 I

L

G

M M K S -21 CAG GAG CAA CCA GCA TGT Q E Q P A C 10 CTG MT MC TAC CTT CGT L N N Y L R

TAT CCT GTG Y P V 30 CCA TAC CTG TGT CAC CTG TAT P Y L C H L Y 60 GAC ATC CAC CAG TCC ACC ATG D I H Q S T M

329

K

GTG CAG AAC V 0 N

Craig,R.K. et al. (1981) Biochem. J. 194, 989-998. Hall,L. et al. (1984) Biochem. J. 222, 561-570. Hall,L. et al. (1984) Eur. J. Biochem. 138, 585-589. Pascall,J.C. and Craig,R.K. (1986) Biotechnol. Appl. Biochem. 8, 172-181. Holt,C. and Sawyer,L. (1988) Prot Engin. 2, 251-259.

K

A

F

L

L

V

V

TGT GGG AAT GAT GAA C G N D E

ACT GCA CCC T A P 40 TAT GTA CCA TCT TTT GTG CTT F V L Y V P S

CAA TAT CAT Q Y H 90 ACC ATC CTT TCT ACT GAT GCC ATC T I L S T D A I 110 ACC CCA GAA GTC TCC TCA CAG TTC T P E V S S Q F 140 ACC CCA GAA ATC TCA GAG TTC ATC T P E I S E F I 170 CCA GAA ATC TCC TCA GAG TTC ATA P E I S S E F I

CAA GCC Q A GCT GCT A A

AGT TAC S Y

N

I

V

A

L

-10 AGA CTG TTT GAA CAA R L F E Q 20 TAC CM AAT AGA GCT Q N R A

T

L

AAA MA K K TCT GTA S V

TGG GCA CAA GGC CAA ATT CCC MG GOG

Q G Q I 70 MA CAC CCT TCA TTT ATG GCC ATT K H P S F M A I 100 CCA GAG CAA ACT CCA GTC TCT GCT P E Q T P V S A 120 ACC CCT GAC ACT TCA GTC CTA GCT L A T P D T S V 150 CCT GAC ACT GCA GTC CCA AGT GAG P D T A V P S E 180 CCC GAG ACC TCC ACA GGC CCA GCC P E T S T G P A

W

A

P

K

G

CTG TCA AAG L S K

GCA CAG CCC A Q P 130 GAG GAG GCC E E A

491

ACA GTG AGC GCT GGG GAC T V S A G D

572

GAG CCC AGA AGA GAG AGC CCC GAG GAC AAT GCT E P R R E S P E D N A 160 ATT GCA TCC GAG AGT GCT GAG GAC ACC TTC TCC I A S E S A E D T F S 210 190 200 ATG GCA TAG MGCAATACGGAGACMTACAGGTTTTGCTGMACCMTGACMTTTCAAACCTTGCTTCAGCCATTTTTCATCTTTATTCMGAGAMATGTGA * M A 213

653 734

838

X56020

Met 98), involved in milk clotting; and (iii) a sequence of about 27 amino acids, repeated three times (residues 127- 153, 154- 179 and 180-207) and showing a high degree of nucleotide similarity, suggesting multiple gene duplication. This latter feature is unique to the guinea-pig x-casein and accounts for the greater size of its mRNA and protein product (4) when compared to those of other species.

GCCAACCAAGCCCAGGCTGGCACAGGAAAAAGGTGCA ATG ATG AAA TCT TTT CTT CTA GTT GTG MT ATA GTG GCA TTA ACT CTG

1

no.

ATC GAT I D

TGTTCACMATTCAGCTCCTGTCTCTTCTCCCTTTACACTTCATACTCATGTCATTTMTTTTATGATGCGCATCACCTTATGATGCTTGCACMTAAAGTCMC