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The 75-kilodalton cytoplasmic Chlamydia trachomatis L2 polypeptide is a DnaK-like protein
S Birkelund1, A G Lundemose, G Christiansen
1Institute of Medical Microbiology, University of Aarhus, Denmark.
Abstract:
The gene coding for the 75-kilodalton cytoplasmic Chlamydia trachomatis L2 polypeptide has been cloned in Escherichia coli, and the nucleotide sequence has been determined. The cloned DNA fragment contained the coding region as well as the putative promoter. The deduced amino acid sequence of the 1,980-base-pair open reading frame revealed 94% homology with a 75-kilodalton protein from C. trachomatis serovar D and 57% homology with the DnaK proteins of E. coli and of Bacillus megaterium, while amino acid homology with human heat shock protein 70 (hsp70) was 42%. The promoter region was identified by computer search and by primer extension of mRNA synthesized in recombinant E. coli. The promoter region which differed from the putative promoter region in serovar D was shown to be a mixed promoter type in which the -10 region showed a regular TATA box configuration while the -35 region showed high homology with heat shock promoters. This mixed promoter was recognized in E. coli.
Insights
Researchers cloned the Chlamydia trachomatis L2 gene in E. coli, revealing a unique heat shock promoter. This finding advances understanding of chlamydial gene regulation and heat shock protein interactions.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Chlamydia trachomatis is an obligate intracellular bacterium causing various human infections.
- Heat shock proteins (HSPs) play crucial roles in cellular stress response and protein folding.
- Understanding chlamydial gene regulation, particularly for stress-related genes, is vital for developing therapeutic strategies.
Purpose of the Study:
- To clone and sequence the gene encoding the 75-kilodalton (kDa) cytoplasmic Chlamydia trachomatis L2 polypeptide.
- To identify and characterize the promoter region of this gene.
- To investigate the homology of the C. trachomatis L2 protein with known heat shock proteins.
Main Methods:
- Gene cloning in Escherichia coli (E. coli).
- Nucleotide sequencing of the cloned DNA fragment.
- Amino acid sequence analysis and homology comparisons using bioinformatics tools.
- Promoter identification via computer search and primer extension of mRNA.
Main Results:
- The 1,980-base-pair open reading frame for the 75-kDa C. trachomatis L2 polypeptide was successfully cloned and sequenced.
- The deduced amino acid sequence showed 94% homology to a similar protein from C. trachomatis serovar D and significant homology to bacterial DnaK proteins (57%) and human heat shock protein 70 (hsp70) (42%).
- A novel mixed-type promoter region was identified, featuring a TATA box (-10 region) and a heat shock promoter-like sequence (-35 region), which was functional in E. coli.
Conclusions:
- The gene for the 75-kDa C. trachomatis L2 protein has been cloned and sequenced.
- The identified promoter is a unique mixed type, suggesting a distinct regulatory mechanism for this gene.
- The homology data provides insights into the functional role of the C. trachomatis L2 protein within the heat shock response pathway.