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Journal of Bacteriology, April 1999, p. 2075-2083, Vol. 181, No. 7
Centre for Advanced Food Studies,
Received 23 September 1998/Accepted 12 January 1999
In the genome of the gram-positive bacterium Lactococcus
lactis MG1363, we have identified three genes (clpC,
clpE, and clpB) which encode Clp proteins
containing two conserved ATP binding domains. The proteins encoded by
two of the genes belong to the previously described ClpB and ClpC
families. The clpE gene, however, encodes a member of a new
Clp protein family that is characterized by a short N-terminal domain
including a putative zinc binding domain
(-CX2CX22CX2C-). Expression of the
83-kDa ClpE protein as well as of the two proteins encoded by
clpB was strongly induced by heat shock and, while
clpC mRNA synthesis was moderately induced by heat, we were
unable to identify the ClpC protein. When we analyzed mutants with
disruptions in clpB, clpC, or clpE,
we found that although the genes are part of the L. lactis
heat shock stimulon, the mutants responded like wild-type
cells to heat and salt treatments. However, when exposed to puromycin,
a tRNA analogue that results in the synthesis of truncated, randomly
folded proteins, clpE mutant cells formed smaller colonies
than wild-type cells and clpB and clpC mutant
cells. Thus, our data suggest that ClpE, along with ClpP, which
recently was shown to participate in the degradation of randomly folded
proteins in L. lactis, could be necessary for
degrading proteins generated by certain types of stress.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Disruption and Analysis of the clpB,
clpC, and clpE Genes in Lactococcus
lactis: ClpE, a New Clp Family in Gram-Positive Bacteria
*
Corresponding author. Present address: Institute
of Veterinary Microbiology, The Royal Veterinary and Agricultural
University, KVL, Stigbøjlen 4, DK-1870 Frederiksberg, Denmark.
Phone: 45 3528 2706. Fax: 45 3528 2757. E-mail:
ingmer{at}biobase.dk.
Journal of Bacteriology, April 1999, p. 2075-2083, Vol. 181, No. 7
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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