Transport of proteins into chloroplasts. Import and maturation of precursors to the 33-, 23-, and 16-kDa proteins of the photosynthetic oxygen-evolving complex.
The 33-, 23-, and 16-kDa proteins of the photosynthetic oxygen-evolving complex are synthesized as precursors in the cytoplasm and transported into the thylakoid lumen of higher plant chloroplasts. In this report we have analyzed the import and maturation of these precursors, using reconstituted protein import assays and partially purified preparations of the processing peptidases involved. Precursors of the 33- and 23-kDa proteins from Spinacia and Triticum aestivum are processed by a stromal peptidase to intermediate forms; polypeptides of similar size are observed during the transport of these precursors and possibly that of the 16-kDa protein, into isolated chloroplasts. Complete maturation of the 33- and 23-kDa proteins is carried out by a thylakoidal peptidase shown previously to be involved in plastocyanin biogenesis. The data support an import mechanism involving successive cleavages by the stromal and thylakoidal processing peptidases.
James
H E
HE
Department of Biological Sciences, University of Warwick, Coventry, United Kingdom.
Bartling
D
D
Musgrove
J E
JE
Kirwin
P M
PM
Herrmann
R G
RG
Robinson
C
C
D002734:Chlorophyll / Q000096:biosynthesis / Q000235:genetics*; D002736:Chloroplasts / Q000378:metabolism*; D007887:Fabaceae / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics*; D010944:Plants / Q000378:metabolism*; D010946:Plants, Medicinal; D011499:Protein Processing, Post-Translational
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D002734:Chlorophyll; D010447:Peptide Hydrolases