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Infection and Immunity, December 1998, p. 5882-5888, Vol. 66, No. 12
Department of Microbiology, Defence Research
Establishment, S-901 82 Umeå, Sweden
Received 29 June 1998/Returned for modification 19 August
1998/Accepted 9 September 1998
A Coxiella burnetii Hsp70 homologue was identified by
using an acid activation in vitro system in which protein synthesis has
been followed by [35S]methionine labeling,
autoradiography, and immunoblotting. The protein was one of those
predominantly labeled, and the immunoblots revealed that it was
recognized by anti-DnaK antibodies. The corresponding gene was
isolated, and its nucleotide sequence was determined and analyzed. A
single open reading frame (ORF) with a size of 1,968 bp was identified.
The ORF encodes a protein containing 656 residues and having a
molecular weight of 70,800. The
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Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of a 71-Kilodalton
Surface-Associated Hsp70 Homologue in Coxiella
burnetii
10 promoter sequence was shown to be
identical with the consensus heat shock
32 promoter
sequence. The base composition at the presumed
35 region revealed an
EcoRI site in the expected region, which is assumed to be
located at the border of the cloned fragment. The gene was expressed in
Escherichia coli as an intact protein. The C. burnetii 71-kDa protein sequence has a high degree of homology to
sequences of the Hsp70 family. A comparison of sequences revealed that
the similarity with Hsp70s from other intracellular bacteria, e.g., Legionella pneumophila and Francisella
tularensis, as well as E. coli DnaK, is more than
80%. The homologous regions are found in the N-terminal and central
parts of the protein sequence, and they include the signature patterns
of the Hsp70 family of proteins. The presence of the 71-kDa protein in
association with the cell wall as well as in the cytoplasm was
demonstrated by the use of immunoelectron microscopy. The dual
localization was verified by Western blot analysis of proteins in
C. burnetii cell fractions, using purified antibodies
directed to the 71-kDa protein.
*
Corresponding author. Mailing address: Department of
Microbiology, Defence Research Establishment, S-901 82 Umeå, Sweden. Phone: 46 90 10 66 61. Fax: 46 90 10 68 01. E-mail:
norlander{at}ume.foa.se.
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