J. Biol. Chem., Vol. 268, Issue 34, 25350-25356, Dec, 1993
Chemotactic methyltransferase promotes adaptation to repellents in Bacillus subtilis
ML Kirsch, AR Zuberi, D Henner, PD Peters, MA Yazdi and GW Ordal
Department of Biochemistry, College of Medicine, University of Illinois, Urbana 61801.
Bacillus subtilis cheRB, which encodes the chemotactic methyltransferase,
has been cloned and sequenced. CheRB is a polypeptide of 256 amino acids,
with a predicted molecular mass of 28 kDa. A comparison of the predicted
amino acid sequence of B. subtilis CheRB with that of Escherichia coli
CheRE demonstrates that the two enzymes share 31% amino acid identity. The
homology was functional in that the expression of cheBB in an E. coli cheRE
null mutant made the bacteria Che+. In contrast to cheRE null mutants which
show a strong smooth swimming bias, cheRB null mutants were predominantly
tumbly. They respond to the addition and subsequent removal of attractant.
They also respond to the addition of repellent but do not adapt; they
resume prestimulus bias on removal of repellent. Tethering analysis of a
culture of a cheRB null mutant revealed two distinct subpopulations, each
demonstrating unique behaviors. One showed a strong clockwise flagellar
rotation bias, whereas the other was more random. The latter phenotype may
be due to a deficiency of CheB and may reflect an interaction of CheB and
CheR. Measurements of CheB activity in the cheR null mutant showed them to
be only 20% of wild type levels. We conclude from this work that CheRB
functions to promote adaptation to repellent stimuli in B. subtilis,
whereas CheRE functions to promote adaptation to attractant stimuli in E.
coli.
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