Evidence for beta-sheet conformation in vesicle-bound peptides derived from the transmembrane bacterial flagellar motor protein MotB from Rhodobactersphaeroides

Circular dichroism experiments show that a 28 residue transmembrane peptide derived from the R. sphaeroides bacterial flagellar motor protein MotB ado pts predominantly beta-sheet conformation when bound within phosphatidylcho line vesicles. A peptide with a mutation at Asp32, which has been shown to destroy proton conductance, is also shown to insert into the model membrane in predominantly beta-sheet conformation, suggesting that it is not the gr oss structural features of the transmembrane region that are disrupted by t his mutation but perhaps only the electrostatic properties of the pore. A t entative structure for a MotB pore is proposed which consists of an eight s tranded beta-barrel.