title: Organization of the thylakoid membrane from the heterotrophic cyanobacterium, Aphanocapsa 6714.
abstract: The polypeptide composition of thylakoid membrane fractions from the heterotrophic cyanobacterium Aphanocapsa 6714 was examined by electrophoretic and immunoblotting procedures. We have identified thylakoid cytochromes f, b6, c-550 and c-553 by tetramethylbenzidine staining of lithium dodecyl sulfate polyacrylamide gels; we also have identified the Rieske Fe-S center protein and subunit 4 of the cytochrome b6/f complex. We have characterized phycobilisomes and active core preparations of PS I and PS II. PS I is comprised of five polypeptides (62 kDa, 14.5 kDa, 10 kDa, and two proteins of less than 10 kDa), and our PS II preparation is highly enriched for three chlorophyll-binding proteins of 48, 45 and 36 kDa. Furthermore, we have resolved the chlorophyll-binding complexes on non-denaturing gels and have determined the polypeptide composition of each chlorophyll-containing band. Three bands are associated with PS I (I, IIa and IIb) and three bands are PS II components (III', IIIa and IIIb) as judged by low-temperature fluorescence emission spectra. Band III' contains a 64 kDa antenna polypeptide, IIIa contains the 48 kDa and 45 kDa polypeptides, and IIIb is comprised solely of a 36 kDa protein. The IIIb apoprotein represents a novel PS II component; its possible role in photochemistry is discussed.
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure*; D002734:Chlorophyll / Q000032:analysis; D000458:Cyanobacteria / Q000648:ultrastructure*; D003580:Cytochromes / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D007163:Immunosorbent Techniques; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000032:analysis*; D010455:Peptides / Q000032:analysis; D045322:Photosynthetic Reaction Center Complex Proteins; D045524:Phycobilisomes; D010940:Plant Proteins / Q000032:analysis
chemical_list: D003580:Cytochromes; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D010455:Peptides; D045322:Photosynthetic Reaction Center Complex Proteins; D045524:Phycobilisomes; D010940:Plant Proteins; D002734:Chlorophyll