Journal of Bacteriology, July 1999, p. 4381-4390, Vol. 181, No. 14
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Environmental Engineering and Science, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305-4020
Received 6 October 1998/Accepted 4 May 1999
Gliding movements of individual isolated Myxococcus
xanthus cells depend on the genes of the A-motility system
(agl and cgl genes). Mutants carrying defects
in those genes are unable to translocate as isolated cells on solid
surfaces. The motility defect of cgl mutants can be
transiently restored to wild type by extracellular complementation upon
mixing mutant cells with wild-type or other motility mutant cells. To
develop a molecular understanding of the function of a Cgl protein in
gliding motility, we cloned the cglB wild-type allele by
genetic complementation of the mutant phenotype. The nucleotide
sequence of a 2.85-kb fragment was determined and shown to encode two
complete open reading frames. The CglB protein was determined to be a
416-amino-acid putative lipoprotein with an unusually high cysteine
content. The CglB antigen localized to the membrane fraction. The
swarming and gliding defects of a constructed
cglB
mutant were fully restored upon complementation with the
cglB wild-type allele. Experiments with a cglB
allele encoding a CglB protein with a polyhistidine tag at the C
terminus showed that this allele also promoted wild-type levels of
swarming and single-cell gliding, but was unable to stimulate
cglB cells to move. Possible functions of CglB as a mechanical component or as a signal protein in single cell gliding are discussed.
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