This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by McMurry, J. L. Articles by Macnab, R. M. Search for Related Content PubMed PubMed Citation Articles by McMurry, J. L. Articles by Macnab, R. M.

Analysis of the Cytoplasmic Domains of Salmonella FlhA and Interactions with Components of the Flagellar Export Machinery

Jonathan L. McMurry, John S. Van Arnam, May Kihara,^* and Robert M. Macnab

Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut

Received 14 June 2004/ Accepted 13 August 2004

Most flagellar proteins are exported via a type III export apparatus which, in part, consists of the membrane proteins FlhA, FlhB, FliO, FliP, FliQ, and FliR and is housed within the membrane-supramembrane ring formed by FliF subunits. Salmonella FlhA is a 692-residue integral membrane protein with eight predicted transmembrane spans. Its function is not understood, but it is necessary for flagellar export. We have created mutants in which potentially important sequences were deleted. FlhA lacking the amino-terminal sequence prior to the first transmembrane span failed to complement and was dominant negative, suggesting that the sequence is required for function. Similar effects were seen in a variant lacking a highly conserved domain (FHIPEP) within a putative cytoplasmic loop. Scanning deletion analysis of the cytoplasmic domain (FlhAc) demonstrated that substantially all of FlhAc is required for efficient function. Affinity blotting showed that FlhA interacts with several other export apparatus membrane proteins. The implications of these findings are discussed, and a model of FlhA within the export apparatus is presented.

Passed away on 7 September 2003.