Identification of the PufQ protein in membranes of Rhodobacter capsulatus.
The PufQ protein has been detected in vivo for the first time by Western blot (immunoblot) analyses of the chromatophore membranes of Rhodobacter capsulatus. The PufQ protein was not visible in Western blots of membranes of a mutant (delta RC6) lacking the puf operon but appeared in membranes of the same mutant to which the pufQ gene had been added in trans. It was also detected in elevated amounts in a mutant (CB1200) defective in two bch genes and unable, therefore, to make bacteriochlorophyll. The extremely hydrophobic nature of the PufQ protein was also apparent in these studies since it was not extracted from chromatophores by 3% (wt/vol) n-octyl-beta-D-glucopyranoside, a procedure which solubilized the reaction center and light-harvesting complexes. During adaptation of R. capsulatus from aerobic to semiaerobic growth conditions (during which time the synthesis of bacteriochlorophyll was induced), the PufQ protein was observed to increase to the level of detection in the developing chromatophore fraction approximately 3 h after the start of the adaptation. The enzyme, S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase, also increased in amount in the developing chromatophore fraction but was present in a cell membrane fraction at the start of the adaptation as well.
Fidai
S
S
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
Hinchigeri
S B
SB
Borgford
T J
TJ
Richards
W R
WR
D000332:Aerobiosis; D000693:Anaerobiosis; D000907:Antibodies, Bacterial / Q000276:immunology; D020130:Bacterial Chromatophores; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls / Q000096:biosynthesis; D015153:Blotting, Western; D002455:Cell Division / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008566:Membranes / Q000737:chemistry; D008780:Methyltransferases / Q000032:analysis; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D016354:Rhodobacter capsulatus / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000276:immunology
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C087270:PufQ protein, Rhodobacter capsulatus; D011993:Recombinant Fusion Proteins; D008780:Methyltransferases; C060234:magnesium-protoporphyrin methyltransferase