POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X ______ Poster #3<br />
FUNCTION OF UNIQUE DOMAINS OF CheA1 FROM A. BRASILENSE IN REGULATING<br />
MULTIPLE CELLULAR BEHAVIORS<br />
Amber N. Bible and Gladys Alexandre<br />
Department <strong>of</strong> Biochemistry, Cellular, and Molecular Biology at the <strong>University</strong> <strong>of</strong> Tennessee,<br />
Knoxville<br />
The alpha-proteobacterium Azospirillum brasilense contains four different chemotaxis<br />
operons. One <strong>of</strong> the 4 Che-like pathways (Che1) encoded within the genome <strong>of</strong> the<br />
alphaproteobacterium A. brasilense was recently shown to regulate changes in motility patterns,<br />
cell-to-cell aggregation (clumping) concomitant with changes in cell length (Bible et al., 2008).<br />
Mutations affecting cheA1 decrease chemotaxis, cell length, but lead to an increase in<br />
clumping relative to the wild type A. brasilense. Interestingly, CheA1 is a hybrid histidine kinase<br />
with two P5-like domains and a REC-like receiver domain at its C-terminus. In addition, the Nterminus<br />
<strong>of</strong> CheA1 comprises a highly conserved polytopic domain <strong>of</strong> unknown function,<br />
suggesting that CheA1 may be a membrane-bound protein. Experimental data indicate that<br />
CheA1 is produced as a membrane-bound protein that localizes to the cell pole, similar to other<br />
Che1 proteins. Noticeably, the polytopic N-terminal domain <strong>of</strong> CheA1 is not required for the<br />
localization <strong>of</strong> CheA1 neither to the cell pole, nor for changes in cell length or cell-to-cell<br />
aggregation but it is essential for wild-type chemotaxis and aerotaxis behaviors. Data obtained<br />
from a combination <strong>of</strong> in-frame deletions <strong>of</strong> the C-terminal domains and site-specific<br />
mutagenesis approaches with behavioral assays suggest that the second P5-like domain <strong>of</strong><br />
CheA1 has a role in modulating changes in cell length. A working model for the functions <strong>of</strong> the<br />
N- and C-terminal domains <strong>of</strong> CheA1 in modulating chemotaxis, aerotaxis, clumping and cell<br />
length changes will be presented in lights <strong>of</strong> recent experimental data.<br />
Bible, A. N., Stephens, B. B., Ortega, D. R., Xie, Z. and G. Alexandre (2008) Function <strong>of</strong> a<br />
chemotaxis-like signal transduction pathway in modulating motility, cell clumping, and cell length<br />
in the alphaproteobacterium Azospirillum brasilense. J Bacteriol 190: 6365-6375.<br />
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