CheY protein

The sensor protein is NtrB (NRn), which is an auto-phosphorylating histidine kinase similar to the CheY protein of bacterial chemotaxis (Fig. 19-5). 

Fumarate was also demonstrated to be a switch factor in eubacteria. Fumarate and the CheY protein are the only cytoplasmic components required for spontaneous motor switching in Escherichia coli and Salmonella typhimurium [43]. 

Figure 34.32 Chemotaxis signaling pathway. Receptors in the plasma membrane initiate a signaling pathway leading to the phosphorylation of the CheY protein. Phosphorylated CheY binds to the flagellar motor and favors clockwise rotation. When an attractant binds to the receptor, this pathway is blocked, and counterclockwise flagellar rotation and, hence, smooth swimming result. When a repellant binds, the pathway is stimulated, leading to an increased concentration of phosphorylated CheY and, hence, more frequent clockwise rotation and tumbling.

Phototaxis in Rb. sphaeroides is triggered by the effects of the photosynthetic machinery on the rate of electron transfer (9). Thus, in contrast to the situation in H. salinarum, phototaxis in Rb. sphaeroides does not involve a dedicated photosensor. The rate of electron transfer is presumably sensed by an as yet unidentified receptor, and relayed into the complex set of Che proteins in Rb. sphaeroides (Fig. 1). Thus, phototaxis responses in Rb. sphaeroides can be regarded as a form of redox taxis and are modulated by factors affecting electron transport, such as the presence or absence of oxygen (19). The Rb. sphaeroides encodes nine transmembrane chemoreceptors (MCPs) and four putative cytoplasmic MCPs, four CheA proteins, and six CheY proteins (20). A number of proteins from this Che system have been shown to be required for phototaxis in Rb. sphaeroides, showing that the signal transduction chains for phototaxis and chemotaxis converge at this level (21). A similar situation holds for phototaxis and chemotaxis in R. centenum (see later). 

Fomaneck MS, Ma L, Cui Q. 2006. Reconciling the old and new view of protein allostery A molecular simulation study of chemotaxis Y protein (CheY). Proteins Struct. Func. Bioinform. 63 846-867. 

Table 11. Constitutively active mutant CheY proteins and active CheY analogs.

As shown in Table 12, many bacterial species do not contain CheZ. It has been suggested that, with the exception of P. aeruginosa, CheZ only exists in enteric bacteria that contain CheAg [494], suggesting that the CheZ-CheAs interaction plays a role in chemotaxis of CheZ-containing species (Section 8.2.8). Species that do not contain CheZ usually possess a few CheY proteins. One or more of the CheY proteins apparently acts as a phosphate sink and thereby fulfills the phosphatase role of CheZ [642, 676]. 

Lukat, G.S., Stock, A.M. and Stock, J.B. (1990). Divalent metal ion binding to the CheY protein and its significance to phosphotransfer in bacterial chemotaxis. 

Stock, A., Koshland, D.E., Jr. and Stock, J. (1985). Homologies between Salmonella typhimurium CheY protein and proteins involved in the regulation of chemotaxis, membrane protein synthesis, and sporulation. Proc. Natl. Acad. Sci. 

Dons, L. Olsen, J.E. Rasmussen, O.F. Characterization of two putative Listeria monocytogenes genes encoding polypeptides homologous to the sensor protein CheA and the response regulator CheY of chemotaxis. DNA Seq., 4, 301-311 (1994)... 

In its active form CheA undergoes autophosphorylation, that is, the phosphorylation of a histidine imidazole group in one of its subunits by the protein kinase active site of an adjacent subunit. The phospho group is then transferred from phospho-CheA to another protein, CheY. Phospho-CheY interacts with the flagellar motor proteins (Chapter 19) periodically causing a reversal of direction of the bacterial flagella. As a result the bacteria tumble and then usually move... 

Figure 19-5 Schematic representation of an important chemotactic system of E. coli, S. typhimurium, and other bacteria. The transmembrane receptor activates the autokinase CheA, which transfers its phospho group to proteins CheY and CheB to form CheY-P and CheB-P. CheY-P regulates the direction of rotation of the flagella, which are distributed over the bacterial surface. CheR is a methyltransferase which methylates glutamate carboxyl groups in the receptor and modulates the CheA activity. CheZ is a phosphatase and CheB-P a methylesterase.

Phytochrome is found not only in higher plants but also in algae, where it controls the movement of chloroplasts,611 and also in cyanobacteria.623 54 Cyano-bacterial phytochromes contain histidine kinase domains, which may function in a two-component system with a response regulator similar to protein CheY of the chemotaxis system in E. coli (Fig. 19-5).624/625 Some nonphotosynthetic bacteria also use bacteriophytochromes for light sensing. In some cases biliverdin (Fig. 24-24) is the chromophore.6253... 

In the absence of 02 the E. coli FNR protein induces proteins of the anaerobic respiration pathways. Nitrate also has its own two-component system that senses nitrate availability and activates transcription of enzymes catalyzing nitrate respiration.162 An expanded two-component system induces sporulation in Bacillus subtilis in response to poor growth conditions.163164 The crystal structure of one of two response regulators (SpoOF) has a structure closely related to that of CheY and the nitrate response regulator NarL. 

Bacterial protein Alba, CheY, acetyl CoA synthetase... 

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