Sequence analysis reveals new membrane anchor of reaction centre-bound cytochromes possibly related to PufX.
Most of the bacterial photosynthetic reaction centres known to date contain a cytochrome subunit with four covalently bound haem groups. In the case of Blastochloris viridis, this reaction centre subunit is anchored in the membrane by a lipid molecule covalently attached to the cysteine which forms the N-terminus of the mature protein after processing by a signal peptidase. We show that posttranslational N-terminal cleavage of the cytochrome subunit does not occur in the aerobic photosynthetic bacterium Roseobacter denitrificans. From sequence analysis of the resulting elongated N-terminus it follows that a transmembrane helix is anchoring the reaction centre-bound cytochrome in the membrane. Comparative sequence analysis strongly suggests that all cytochrome subunits lacking the lipid coupling cysteine share this structural feature. Comparison of the N-terminal segment of the cytochrome subunit of Roseobacter denitrificans with the sequences of the PufX proteins from Rhodobacter sphaeroides and Rhodobacter capsulatus suggests a phylogenetic relation.
Hucke
Oliver
O
Institut für Physikalische Chemie, Albertstr. 23a, Universität Freiburg, D-79104 Freiburg, Germany.
Schiltz
Emile
E
Drews
Gerhart
G
Labahn
Andreas
A
D000595:Amino Acid Sequence; D001419:Bacteria; D001420:Bacteria, Aerobic; D001426:Bacterial Proteins / Q000235:genetics*; D003580:Cytochromes / Q000235:genetics*; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D010802:Phylogeny; D021122:Protein Subunits / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D003580:Cytochromes; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D021122:Protein Subunits; C088749:PufX protein, Rhodobacter