Gene sequence for the 9 kDa component of Photosystem II from the cyanobacterium Phormidium laminosum indicates similarities between cyanobacterial and other leader sequences.
A 9 kDa polypeptide which is loosely attached to the inner surface of the thylakoid membrane and is important for the oxygen-evolving activity of Photosystem II in the thermophilic cyanobacterium Phormidium laminosum has been purified, a partial amino acid sequence obtained and its gene cloned and sequenced. The derived amino acid sequence indicates that the 9 kDa polypeptide is initially synthesised with an N-terminal leader sequence of 44 amino acids to direct it across the thylakoid membrane. The leader sequence consists of a positively charged N-terminal region, a long hydrophobic region and a typical cleavage site. These features have analogous counterparts in the "thylakoid-transfer domain" of lumenal polypeptides from chloroplasts of higher plants. These findings support the view of the proposed function of this domain in the two-stage processing model for import of lumenal, nuclear-encoded polypeptides. In addition, there is striking primary sequence homology between the leader sequences of the 9 kDa polypeptide and those of alkaline phosphatase (from the periplasmic space of Escherichia coli) and, particularly in the region of the cleavage site, the 16 kDa polypeptide of the oxygen-evolving apparatus in the thylakoid lumen of spinach chloroplasts.
Wallace
T P
TP
Department of Biochemistry, University of Cambridge, UK.
Stewart
A C
AC
Pappin
D
D
Howe
C J
CJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D002734:Chlorophyll / Q000235:genetics*; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics*; D004247:DNA / Q000235:genetics; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics*; D021382:Protein Sorting Signals / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D021382:Protein Sorting Signals; D002734:Chlorophyll; D004247:DNA