Complete processing of a small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase from pea requires the amino acid sequence Ile-Thr-Ser.
Chloroplast import and processing of two precursor proteins with mutations in the carboxyl-terminal region of the transit peptide were examined in vitro. Deletion mutations were introduced into the 57-amino acid transit peptide of a chloroplast protein, the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, from pea. A mutant, PSd48/57, in which nine carboxyl-terminal amino acids of the transit peptide had been deleted, was imported and processed to a series of 13- to 18-kDa polypeptides including the 14-kDa mature small subunit. In contrast, processing of a mutant, PSd45/57, in which an additional three amino acids had been removed, resulted in a series of polypeptides which did not include the mature small subunit. Whereas PSd48/57 was imported as efficiently as the wild-type precursor, import of PSd45/57 was only 25% as efficient as that of the authentic precursor. The mutant precursor proteins PSd48/57 and PSd45/57 are distinguished by a three-amino acid sequence, Ile-Thr-Ser, located in the carboxyl-terminal region of the transit peptide. We show that all or part of this sequence is required for correct processing.
Wasmann
C C
CC
Department of Biochemistry, University of Arizona, Tucson 85721.
Reiss
B
B
Bohnert
H J
HJ
D000595:Amino Acid Sequence; D002872:Chromosome Deletion; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D007887:Fabaceae; D046911:Macromolecular Substances; D008970:Molecular Weight; D009154:Mutation; D010446:Peptide Fragments / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D010946:Plants, Medicinal; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*
D004792:Enzyme Precursors; D046911:Macromolecular Substances; D010446:Peptide Fragments; D012273:Ribulose-Bisphosphate Carboxylase