SummaryVibrio cholerae has three sets of chemotaxis-related signaling proteins, of which only System II has been shown to be involved in chemotaxis. Here, we examined localization of green fluorescent protein (GFP)-fused components of System I. The histidine kinase (CheA1) and the adaptor (CheW0) of System I localized to polar and lateral membrane regions with standing incubation (microaerobic conditions), but their localization was lost after shaking (aerobic conditions). A transmembrane receptor of System I also showed polar and lateral localization with standing incubation. By contrast, GFP-fused components of System II localized constitutively to the flagellated pole. Nitrogen gas, sodium azide or carbonylcyanide m-chlorophenylhydrazone induced localization of CheA1-GFP even with shaking incubation, suggesting that the localization is controlled in response to changes in energy metabolism. Fluorescently labeled tetracysteine-tagged CheA1 also showed azideinduced localization, arguing against artifactual effects of GFP fusions. These results suggest that System I components are assembled into the supramolecular signaling complex in response to reduced cellular energy states, raising the possibility that the System I complex plays a role in sensing and signaling under microaerobic environments, such as in the host intestine.

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Actin iilament dynamics are crucia[ in eell rnotility. The dynamics ef actin fi]aments und its asscmblies are based on dynamit ehangcs in thc structure of the actin monomer. Recently, lvc dctccted confermational changes of actin molecules labeled with tetrarnethy]rhodamine as a donor at Gln-41 in the DNase-I binding loop and ICS as an acceptor at Cys-374 neur the C terminus in the filamcnt using single-molecLLIe fluerescence resonanee energy transfer (FRET> (Kozuku,et al, Nature chemical bielogy. 2006). The results sliowed that actin extsrs in two major conformational states and can switch

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