Reference "The A- and B-chains of carboxypeptidase I from germinated barley originate from a single precursor polypeptide"

Reference ID

8608

Title

The A- and B-chains of carboxypeptidase I from germinated barley originate from a single precursor polypeptide

Source

The Journal of biological chemistry, 1988, vol. 263, pp. 11106-11110

Authors (2)

Doan-N-P

Fincher-G-B

Abstract

Carboxypeptidase I from germinated barley (Hordeum vulgare) grain consists of
two peptide chains linked by disulfides; the A- and B-chains contain 266 and 148
amino acid residues, respectively (Sorensen, S. B., Breddam, K., and Svendsen,
I. (1986) Carlsberg Res. Commun. 51, 475-485). A cDNA library prepared from mRNA
isolated from scutella of 2-day germinated barley has now been screened with a
mixed oligonucleotide encoding a peptide fragment of the A-chain. Nucleotide
sequence analysis of a 1443-nucleotide pair cDNA clone revealed that both chains
of the enzyme are translated from a single mRNA. The coding region of the A-
chain is located at the 5'-end of the cDNA and is separated from the B-chain
coding region by a 165-nucleotide pair linking region. The B-chain coding region
is followed by a stop codon, a 187-nucleotide pair 3'-untranslated sequence, and
a short polyadenylic acid tail. The results indicate that the A- and B-chains of
barley carboxypeptidase I arise by endoproteolytic excision of a 55-residue
linker peptide from a single precursor polypeptide chain. The putative linker
peptide is rich in proline, lysine, and arginine residues, has an apparent pI of
11.9, and appears to be excised by cleavage of peptide bonds on the COOH-
terminal side of serine residues.