Molecular cloning of cDNA encoding potato amyloplast alpha-glucan phosphorylase and the structure of its transit peptide.
The type L isozyme of potato tuber alpha-glucan phosphorylase [EC 2.4.1.1], a dimer of 104-kDa subunits, is compartmentalized in the amyloplast. We have cloned a nearly full-length cDNA encoding this isozyme from a cDNA library of immature potato tuber. The sequence was supplemented by a partial genomic clone. The transcription initiation site was identified by a primer extension experiment to be 43 bases upstream from the translation initiation ATG codon. The message encodes a polypeptide of 966 amino acid residues, of which 50 residues constitute an N-terminal extended peptide and 916 residues make up the mature protein. In the mature protein region, the nucleotide sequence is consistent with the chemically determined amino acid sequence (Nakano, K. & Fukui, T. (1986) J. Biol. Chem. 261, 8230-8236). The N-terminal extension bears characteristic features of the transit peptides of nuclear-encoded chloroplastic proteins, and is therefore regarded as a transit peptide for the amyloplast. This peptide is rich in basic amino acids (5 arginines, 3 lysines, and 5 histidines) and hydroxylic amino acids (7 serines and 5 threonines), but lacks acidic amino acids. It is therefore classified as one of the most basic transit peptides so far reported.
Nakano
K
K
Institute of Scientific and Industrial Research, Osaka University.
Mori
H
H
Fukui
T
T
D001483:Base Sequence; D002736:Chloroplasts / Q000201:enzymology*; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics*; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D006005:Phosphorylases / Q000032:analysis / Q000235:genetics*; D011061:Poly A / Q000032:analysis; D012313:RNA / Q000032:analysis; D011198:Solanum tuberosum / Q000201:enzymology*; D014158:Transcription, Genetic
D010455:Peptides; D011061:Poly A; D012313:RNA; D004247:DNA; D006005:Phosphorylases