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J. Bacteriol., 05 1997, 2963-2968, Vol 179, No. 9
A Brooun, W Zhang and M Alam
Signal transduction in the archaeon Halobacterium salinarium is mediated by
a family of 13 soluble and membrane-bound transducers. Here, we report the
primary structure and functional analysis of one of the smallest
halobacterial putative transducers, HtrXI. Hydropathy plot analysis of the
primary structure predicts no membrane-spanning segments in HtrXI. The
fractionation of the H. salinarium proteins confirmed that HtrXI is a
soluble protein. Capillary assay with an HtrXI deletion mutant and a
complemented strain revealed that this soluble transducer is involved in
Asp and Glu taxis. In vivo analysis of the methylesterase activity of the
htrXI-1 deletion mutant suggests that HtrXI plays an important role in the
adaptation of the chemotactic responses to His, Asp, and Glu, which are
attractants for halobacteria. Stimulation by Asp and Glu causes
demethylation of HtrXI and of another putative transducer, HtrVII. But
addition of His to halobacterial cells increases HtrXI methylation together
with that of other putative transducers. In the absence of HtrXI,
stimulation by either Glu or His does not decrease or increase the
methylation of any putative transducers. Therefire, the HtrXI transducer
appears to have a complex role in chemotaxis signal transduction.
Copyright © 1997, American Society for Microbiology
Primary structure and functional analysis of the soluble transducer protein HtrXI in the archaeon Halobacterium salinarium
Department of Microbiology, University of Hawaii, Honolulu.
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