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J. Bacteriol., 12 1995, 6874-6880, Vol 177, No. 23
Y Lin and JN Hansen
The ability to respond to osmotic stress by osmoregulation is common to
virtually all living cells. Gram-negative bacteria such as Escherichia coli
and Salmonella typhimurium can achieve osmotolerance by import of
osmoprotectants such as proline and glycine betaine by an import system
encoded in an operon called proU with genes for proteins ProV, ProW, and
ProX. In this report, we describe the discovery of a proU-type locus in the
gram-positive bacterium Bacillus subtilis. It contains four open reading
frames (ProV, ProW, ProX, and ProZ) with homology to the gram-negative ProU
proteins, with the B. subtilis ProV, ProW, and ProX proteins having
sequence homologies of 35, 29, and 17%, respectively, to the E. coli
proteins. The B. subtilis ProZ protein is similar to the ProW protein but
is smaller and, accordingly, may fulfill a novel role in osmoprotection.
The B. subtilis proU locus was discovered while exploring the chromosomal
sequence upstream from the spa operon in B. subtilis LH45, which is a
subtilin-producing mutant of B. subtilis 168. B. subtilis LH45 had been
previously constructed by transformation of strain 168 with linear DNA from
B. subtilis ATCC 6633 (W. Liu and J. N. Hansen, J. Bacteriol.
173:7387-7390, 1991). Hybridization experiments showed that LH45 resulted
from recombination in a region of homology in the proV gene, so that the
proU locus in LH45 is a chimera between strains 168 and 6633. Despite being
a chimera, this proU locus was fully functional in its ability to confer
osmotolerance when glycine betaine was available in the medium.(ABSTRACT
TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Characterization of a chimeric proU operon in a subtilin-producing mutant of Bacillus subtilis 168
Department of Chemistry and Biochemistry, University of Maryland, College Park 20742, USA.
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