POSTERS - BLAST X - University of Utah

BLAST X ______ Poster #3
FUNCTION OF UNIQUE DOMAINS OF CheA1 FROM A. BRASILENSE IN REGULATING
MULTIPLE CELLULAR BEHAVIORS
Amber N. Bible and Gladys Alexandre
Department of Biochemistry, Cellular, and Molecular Biology at the University of Tennessee,
Knoxville
The alpha-proteobacterium Azospirillum brasilense contains four different chemotaxis
operons. One of the 4 Che-like pathways (Che1) encoded within the genome of the
alphaproteobacterium A. brasilense was recently shown to regulate changes in motility patterns,
cell-to-cell aggregation (clumping) concomitant with changes in cell length (Bible et al., 2008).
Mutations affecting cheA1 decrease chemotaxis, cell length, but lead to an increase in
clumping relative to the wild type A. brasilense. Interestingly, CheA1 is a hybrid histidine kinase
with two P5-like domains and a REC-like receiver domain at its C-terminus. In addition, the Nterminus
of CheA1 comprises a highly conserved polytopic domain of unknown function,
suggesting that CheA1 may be a membrane-bound protein. Experimental data indicate that
CheA1 is produced as a membrane-bound protein that localizes to the cell pole, similar to other
Che1 proteins. Noticeably, the polytopic N-terminal domain of CheA1 is not required for the
localization of CheA1 neither to the cell pole, nor for changes in cell length or cell-to-cell
aggregation but it is essential for wild-type chemotaxis and aerotaxis behaviors. Data obtained
from a combination of in-frame deletions of the C-terminal domains and site-specific
mutagenesis approaches with behavioral assays suggest that the second P5-like domain of
CheA1 has a role in modulating changes in cell length. A working model for the functions of the
N- and C-terminal domains of CheA1 in modulating chemotaxis, aerotaxis, clumping and cell
length changes will be presented in lights of recent experimental data.
Bible, A. N., Stephens, B. B., Ortega, D. R., Xie, Z. and G. Alexandre (2008) Function of a
chemotaxis-like signal transduction pathway in modulating motility, cell clumping, and cell length
in the alphaproteobacterium Azospirillum brasilense. J Bacteriol 190: 6365-6375.
54