(152e) Functional Proteomic Approach for Ion-Related Outer Membrane Proteins

Outer membrane (Om) proteins play key role in response to environmental changes in Gram-negative bacteria. Here we introduce the progress on functional proteome responded to iron and Na ions.

Iron is an essential element for bacterial growth. The Om proteins of Gram-negative bacteria play an important role in overcoming the conditions of poor iron availability in the host and natural environments. We undertook a comparative analysis on a sarcosine-insoluble fraction of E. coli K-12 cultured in LB medium with or without limited iron by 2-DE proteomic methodologies. Three proteins, OmpW, OmpX and Tsx, related to iron homeostasis first reported here were further investigated. Importantly, our further proteomic studies reveal a number of previously unrecognized a membrane-interacting multi-protein complex, which may include OmpW, Frd (A, B, C and D), Opd1, Slp and YbjP. Of the eight proteins, OmpW and FrdB are iron-related proteins and bind together. The multi-protein complex is disassociated at 200 ìmol DIP, and OmpW and FrdB mutants show significantly physiological changes.

Bacteria can shift between the ambient seawater and hosts, suggesting the existence of proteins rapidly responding to salt concentrations. In our study, proteomics methodologies were applied to screen OMPs related to salt stress in V. parahaemolyticus, V. alginoticus, P. damsela. OmpW and OmpV were determined in the response in these bacteria as OmpC and OmpF did in E. coli. Furthermore, the two genes were overexpressed in E. coli and complemented in V. paraheamolyticus mutants. The ability in salt-tolerance was elevated in the bacteria overexpressed OmpW and reduced in the cells overexpressed OmpV. V. paraheamolytixus mutants could recover their responses to environmental salt concentrations when they were complemented by OmpW and OmpV of the three cells. These findings indicate that OmpW and OmpV are required for environmental salt regulation in these bacteria.