Rhodobacter sphaeroides WS8 expresses a polypeptide that is similar to MotB of Escherichia coli.

A gene which complements a paralyzed flagellar mutant of Rhodobacter sphaeroides was sequenced. The derived protein sequence has similarity to MotB. R. sphaeroides MotB lacks the C-terminal peptidoglycan-binding motif of other MotB proteins. This divergence of sequence may reflect the unusual, unidirectional, stop-start action of the R. sphaeroides flagellar motor.