The ability of most bacterial flagellar motors to reverse the direction of rotation is crucial for efficient chemotaxis. In Escherichia coli, motor reversals are mediated by binding of phosphorylated chemotaxis protein CheY to components of the flagellar rotor, FliM and FliN, which induces a conformational switch of the flagellar C-ring. Here, we show that for Shewanella putrefaciens, Vibrio parahaemolyticus and likely a number of other species an additional transmembrane protein, ZomB, is critically required for motor reversals as mutants lacking ZomB exclusively exhibit straightforward swimming also upon full phosphorylation or overproduction of CheY.
View Article and Find Full Text PDFSpatiotemporal regulation of cell polarity plays a role in many fundamental processes in bacteria and often relies on 'landmark' proteins which recruit the corresponding clients to their designated position. Here, we explored the localization of two multi-protein complexes, the polar flagellar motor and the chemotaxis array, in Shewanella putrefaciens CN-32. We demonstrate that polar positioning of the flagellar system, but not of the chemotaxis system, depends on the GTPase FlhF.
View Article and Find Full Text PDFThe bacterial RNA-binding protein Hfq functions in post-transcriptional regulation of gene expression. There is evidence in a range of bacteria for specific subcellular localization of Hfq; however, the mechanism and role of Hfq localization remain unclear. Cyanobacteria harbour a subfamily of Hfq that is structurally conserved but exhibits divergent RNA binding sites.
View Article and Find Full Text PDFCph2 from the cyanobacterium Synechocystis sp. PCC 6803 is a hybrid photoreceptor that comprises an N-terminal module for red/far-red light reception and a C-terminal module switching between a blue- and a green-receptive state. This unusual photoreceptor exerts complex, light quality-dependent control of the motility of Synechocystis sp.
View Article and Find Full Text PDFThis communication identifies, for the first time, a receptor protein for signal perception from the P(II) signal transduction protein in the cyanobacterium Synechococcus elongatus. P(II), a phosphoprotein that signals the carbon/nitrogen status of the cells, forms a tight complex with the key enzyme of the arginine biosynthetic pathway, N-acetylglutamate (NAG) kinase. In complex with P(II), the catalytic activity of NAG kinase is strongly enhanced.
View Article and Find Full Text PDFThis communication presents a short outline of the current knowledge on the molecular basis of P(II) signal transduction in unicellular cyanobacteria with respect to the perception of environmental stimuli. First, the general characteristics of the P(II) signalling system in unicellular cyanobacteria are presented, the hallmark of which is modification by serine-phosphorylation, as compared to the paradigmatic P(II) signal transduction system in proteobacteria, which is based on tyrosyl-uridylylation. Then, the focus is turned on the signals controlling P(II) phosphorylation state.
View Article and Find Full Text PDFThe family of PII signal transduction proteins consists of one of the most highly conserved signalling proteins in nature. The cyanobacterial PII homologue transmits signals on the nitrogen and carbon status of the cells through phosphorylation of a seryl residue. Recently, we identified a protein phosphatase 2C (PP2C) homologue from the cyanobacterium Synechocystis PCC 6803, termed PphA, to be the cellular phospho-PII (PII-P) phosphatase.
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