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Infect Immun, March 1998, p. 1167-1173, Vol. 66, No. 3
Department of Microbiology and Immunology,
University of Tennessee, Memphis, Tennessee 38163
Received 8 October 1997/Returned for modification 19 November
1997/Accepted 30 December 1997
The EUO gene (for early upstream open reading frame) of
Chlamydia psittaci was previously found to be transcribed
better at 1 than at 24 h postinfection. We found that the EUO gene
encodes a minor protein that is expressed within 1 h of infection
of host cells with C. psittaci 6BC but that protein
quantity peaks during the logarithmic growth phase of reticulate bodies
(RBs), declines late in the infection (after 20 h) when RBs
reorganize into elementary bodies (EBs), and is absent in infectious
EBs. EUO protein lacks homology to known proteins but does contain a
putative helix-turn-helix motif. We found that recombinant EUO binds to
DNA in vitro with a relatively broad specificity. Using the bp
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of a Chlamydia psittaci
DNA Binding Protein (EUO) Synthesized during the Early and Middle
Phases of the Developmental Cycle
200 to
+67 promoter region of the cysteine-rich envelope protein
(crp) operon as a model, we show that EUO protein
preferentially binds to AT-rich sequences and protects crp
DNA from DNase I from approximately bp
60 to
9. We also found that
native EUO protein in extracts of RBs binds to the promoter region of
the crp operon, demonstrating that the DNA binding property
of EUO protein is not an artifact of recombinant methods. Although EUO
protein appears to bind to the crp operon with high
affinity in vitro (Kd of about 15 nM), it is
not known whether the protein binds the crp DNA in vivo.
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of Tennessee, Memphis, TN
38163. Phone: (901) 448-4664. Fax: (901) 448-8462. E-mail:
thatch{at}utmem1.utmem.edu.
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