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Appl. Environ. Microbiol., 05 1997, 1777-1784, Vol 63, No. 5
T Iizumi and K Nakamura
The dnaK gene of an ammonia-oxidizing bacterium, Nitrosomonas europaea, was
cloned and sequenced. It was found that the dnaK gene product was highly
homologous to previously analyzed dnaK gene products from other organisms
at the amino acid level. Two partial open reading frames located upstream
and downstream of the dnaK gene were also found and identified as grpE and
dnaJ genes, respectively, by the predicted amino acid homology of their
gene products to other bacterial GrpE and DnaJ proteins. Transcription of
the dnaK gene was strongly induced by a heat shock from 30 to 37 degrees C.
An analysis of the expression of the dnaK gene fused to the lacZ
translational reporter gene also showed eightfold increase in
beta-galactosidase activity after the heat shock induction. Heat-inducible
transcription start sites of the dnaK gene, revealed by primer extension
analysis, were located 16 and 17 nucleotides upstream from the
translational start codon of the dnaK gene, and the predicted promoter
sequence showed a homology to the consensus sequence of sigma 32-dependent
heat shock promoters of gram- negative bacteria. The upstream region of the
dnaK gene did not contain the inverted repeat structure that was involved
in the regulation of the heat shock gene of several gram-negative and
gram-positive bacteria. Therefore, we conclude that the heat shock
regulatory mechanism of the N. europaea dnaK gene may be similar to the
sigma 32- dependent mechanism observed in other gram-negative bacteria.
Copyright © 1997, American Society for Microbiology
Cloning, nucleotide sequence, and regulatory analysis of the Nitrosomonas europaea dnaK gene
Kurita Central Laboratories, Kurita Water Industries Ltd., Atsugi, Japan.
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