Features of MotA Proton Channel Structure Revealed by Tryptophan-Scanning Mutagenesis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 92; no. 17; pp. 7946 - 7950
• Main Authors: Sharp, Leslie L., Zhou, Jiadong, Blair, David F.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 15.08.1995; National Acad Sciences; National Academy of Sciences
• Subjects: Amino Acid Sequence; Bacteria; Bacterial Proteins - biosynthesis; Bacterial Proteins - chemistry; Biochemistry; Cell Membrane - metabolism; Cell membranes; Cell Movement; Cloning, Molecular; Escherichia coli; Escherichia coli - metabolism; Escherichia coli - physiology; Flagella - physiology; Genetic mutation; Hydrophobicity; Lipids; Macromolecular Substances; Membranes; Models, Structural; Molecular Sequence Data; Mutagenesis; Mutagenesis, Site-Directed; Mutant proteins; P branes; Plasmids; Protein Structure, Secondary; Proteins; Protons; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Restriction Mapping; Sequence Homology, Amino Acid; Tryptophan
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.92.17.7946

The MotA protein of Escherichia coli is a component of the flagellar motors that functions in transmembrane proton conduction. Here, we report several features of MotA structure revealed by use of a mutagenesis-based approach. Single tryptophan residues were introduced at many positions within the four hydrophobic segments of MotA, and the effects on function were measured. Function was disrupted according to a periodic pattern that implies that the membrane-spanning segments are α-helices and that identifies the lipid-facing parts of each helix. The results support a hypothesis for MotA structure and mechanism in which water molecules form most of the proton-conducting pathway. The success of this approach in studying MotA suggests that it could be useful in structure-function studies of other integral membrane proteins.