Deletion of the 6-kDa subunit affects the activity and yield of the bc1 complex from Rhodovulum sulfidophilum.
The cytochrome bc1 complex from Rhodovulum sulfidophilum purifies as a four-subunit complex: the cytochrome b, cytochrome c1 and Rieske iron-sulphur proteins, which are encoded together in the fbc operon, as well as a 6-kDa protein. The gene encoding the 6-kDa protein, named fbcS, has been identified. It is located within the sox operon, which encodes the subunits of sarcosine oxidase. The encoded 6-kDa protein is very hydrophobic and is predicted to form a single transmembrane helix. It shows no sequence homology to any known protein. The gene has been knocked-out of the genome and a three-subunit complex can be purified. This deletion leads to a large reduction in the yield of the isolated complex and in its activity compared to wild-type. The high quinone content found in the wild-type complex is, however, maintained after removal of the 6-kDa protein. Surprisingly, a fourth subunit of approximately 6 kDa is again found to copurify with the Rhv. sulfidophilum bc1 complex when only the fbc operon is expressed heterologously in a near-relative, Rhodobacter capsulatus, which lacks this small subunit in its own bc1 complex.
Rodgers
S
S
European Molecular Biology Laboratory, Structural Biology Programme, Heidelberg, Germany.
Moser
C
C
Martinez-Julvez
M
M
Sinning
I
I
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002874:Chromosome Mapping; D014450:Electron Transport Complex III / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D011995:Recombination, Genetic; D016992:Rhodobacter / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000235:genetics
D001426:Bacterial Proteins; C411805:fbcS protein, Rhodovulum sulfidophilum; D014450:Electron Transport Complex III