Evidence for β-sheet conformation in vesicle-bound peptides derived from the transmembrane bacterial flagellar motor protein MotB from Rhodobacter sphaeroides

Abstract

Circular dichroism experiments show that a 28 residue transmembrane peptide derived from the R. sphaeroides bacterial flagellar motor protein MotB adopts predominantly β-sheet conformation when bound within phosphatidylcholine 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 β-sheet conformation, suggesting that it is not the gross structural features of the transmembrane region that are disrupted by this mutation but perhaps only the electrostatic properties of the pore. A tentative structure for a MotB pore is proposed which consists of an eight stranded β-barrel.