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International Journal of Microbiology
Volume 2010, Article ID 589391, 5 pages
Research Article

Bacterial Adaptor Membrane Fusion Proteins and the Structurally Dissimilar Outer Membrane Auxiliary Proteins Have Exchanged Central Domains in -Proteobacteria

Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA

Received 10 December 2009; Accepted 31 January 2010

Academic Editor: Isabel Sá-Correia

Copyright © 2010 Anthony Y. Xiao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Transport systems frequently include auxiliary proteins that perform subfunctions within the transporter protein complex. Two such proteins found in Gram-negative bacteria are the Membrane Fusion Proteins (MFPs) and the Outer Membrane Auxiliary (OMA) proteins. We here demonstrate that OMAs present in -proteobacteria (but not in other bacterial types) contain a long -helical region that is homologous to corresponding regions in the MFPs. The results suggest that during their evolution, OMAs, specifically from -proteobacteria, exchanged their own -helical domain for one derived from an MFP. The structural and functional implications of these findings are discussed.