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Chlamydia trachomatis developmentally regulated protein is homologous to eukaryotic histone H1
1Department of Pathology, University of Texas Medical Branch, Galveston 77550.
Abstract:
Chlamydiae are prokaryotic obligate intracellular parasites that undergo a biphasic life cycle involving an infectious, extracellular form known as elementary bodies and an intracellular, replicating form termed reticulate bodies. We have purified from Chlamydia trachomatis a very basic elementary body-specific protein with an apparent molecular mass of 18 kDa, determined its N-terminal amino acid sequence, and cloned the encoding gene. Sequence analysis of the cloned gene revealed some remarkable properties for its expressed product, including a high lysine content (29%), a correspondingly high pI, and significant homology to the H1 class of eukaryotic histones. Furthermore, a monoclonal antibody to this chlamydial histone analog, termed Hc1, displayed immunoblot and antinuclear specificity suggestive of cross-reactivity to H1 histones. The gene was expressed only during the late stages of the chlamydial life cycle concomitant with the reorganization of chlamydial reticulate bodies into elementary bodies, suggesting that the Hc1 protein plays a role in the condensation of chlamydial chromatin during intracellular differentiation.
Insights
Researchers discovered a histone-like protein (Hc1) in Chlamydia trachomatis elementary bodies. This protein is crucial for chromatin condensation during the bacteria
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Chlamydiae are obligate intracellular bacteria with a complex biphasic life cycle.
- This cycle involves distinct elementary bodies (extracellular, infectious) and reticulate bodies (intracellular, replicating).
- Understanding the molecular mechanisms of Chlamydial differentiation is key to controlling infections.
Purpose of the Study:
- To identify and characterize novel proteins specific to Chlamydia trachomatis elementary bodies.
- To investigate the function of a newly identified basic protein in the bacterial life cycle.
Main Methods:
- Purification of an 18 kDa elementary body-specific protein from Chlamydia trachomatis.
- Determination of the N-terminal amino acid sequence and cloning of the encoding gene.
- Sequence analysis, protein expression analysis, and monoclonal antibody production for specificity testing.
Main Results:
- An 18 kDa elementary body-specific protein, named Hc1, was purified and its gene cloned.
- Sequence analysis revealed Hc1 has high lysine content and homology to eukaryotic H1 histones.
- Monoclonal antibodies to Hc1 showed cross-reactivity with eukaryotic H1 histones.
Conclusions:
- The Hc1 protein functions as a histone analog in Chlamydia trachomatis.
- Hc1 expression coincides with the transition from reticulate bodies to elementary bodies.
- Hc1 likely plays a critical role in chromatin condensation during Chlamydial intracellular differentiation.