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Journal of Bacteriology, March 2001, p. 1680-1687, Vol. 183, No. 5
Departamento de Genética Molecular,
Instituto de Fisiología Celular,1 and
Departamento de Biología Molecular, Instituto de
Investigaciones Biomédicas,2 UNAM, 04510 México D.F., México
Received 5 October 2000/Accepted 13 December 2000
In this work we identified the flgE gene encoding the
flagellar hook protein from Rhodobacter sphaeroides. Our
results show that this gene is part of a flagellar cluster that
includes the genes flgB, flgC, flgD, flgE, and
flgF. Two different types of mutants in the
flgE gene were isolated, and both showed a
Fla
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.5.1680-1687.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
The Hook Gene (flgE) Is Expressed from the
flgBCDEF Operon in Rhodobacter sphaeroides: Study
of an flgE Mutant
phenotype, indicating the functionality of this
sequence. Complementation studies of these mutant strains suggest that
flgE is included in a single transcriptional unit that
starts in flgB and ends in flgF. In agreement
with this possibility, a specific transcript of approximately 3.5 kb
was identified by Northern blot. This mRNA is large enough to represent
the complete flgBCDEF operon. FlgE showed a relatively high
proline content; in particular, a region of 12 amino acids near the N
terminus, in which four prolines were identified. Cells expressing a
mutant FlgE protein lacking this region showed abnormal swimming
behavior, and their hooks were curved. These results suggest that this
region is involved in the characteristic quaternary structure of the
hook of R. sphaeroides and also imply that a straight
hook, or perhaps the rigidity associated with this feature, is
important for an efficient swimming behavior in this bacterium.
*
Corresponding author. Mailing address: Departamento de
Genética Molecular, Instituto de Fisiología Celular,
UNAM, Apdo. Postal 70-243, México D.F., México. Phone:
(525) 622-56-03. Fax: (525) 616-22-82. E-mail:
gdreyfus{at}ifisiol.unam.mx.
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