Histidine kinases and response regulators of Halobacterium salinarum

The genome of Halobacterium salinarum strain R1 was sequenced in our department. With these data we are able to perform BLAST searches against appropriate databases, e.g. SMART and Pfam.

Click here for a general introduction of two-component systems.

Figure 1 shows a compilation of all histidine kinases (HK) of H. salinarum identified by sequence homology. On the right side, the C-terminal part of the proteins, the histidine kinase domain (the two green signs) can be found in all candidates but CheA, which is an exception in terms of its final regulation target. The diverse signs on the left side of the graphics code for several signal detecting domains. A good overview about such detection domains of histidine kinases can be found in Galperin et al. (2001).


Fig. 1: Domain organization of histidine kinases of H. salinarum. Graphics generated by the SMART database.

Interestingly H. salinarum has much less response regulators (RR) than histidine kinases. This is very uncommon, because nearly all HK found to date have an affiliated RR. The five proteins consisting only of a response regulator domain are composed in figure 2. In addition to them there are two HK carrying a RR domain on their N-terminal ends (OE4283R and OE7042R in figure 1).

Fig. 2: Response regulator proteins of H. salinarum. Graphics generated by the SMART database.

References

Galperin, M.Y., Nikolskaya, A.N., Koonin, E.V. (2001)
Novel domains of the prokaryotic two-component signal transduction systems.
FEMS Microbiol. Letters, 203, 11-21

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