Related Experiment Video
Updated: Jun 14, 2026
Forward Genetic Approaches in Chlamydia trachomatis
Published on: October 23, 2013
Biological characterization of Chlamydia trachomatis plasticity zone MACPF domain family protein CT153
Lacey D Taylor1, David E Nelson, David W Dorward
1Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
Abstract:
Chlamydia trachomatis strains are obligate intracellular human pathogens that share near genomic synteny but have distinct infection and disease organotropisms. The genetic basis for differences in the pathogen-host relationship among chlamydial strains is linked to a variable region of chlamydial genomes, termed the plasticity zone (PZ). Two groups of PZ-encoded proteins, the membrane attack complex/perforin (MACPF) domain protein (CT153) and members of the phospholipase D-like (PLD) family, are related to proteins that modify membranes and lipids, but the functions of CT153 and the PZ PLDs (pzPLDs) are unknown. Here, we show that full-length CT153 (p91) was present in the elementary bodies (EBs) of 15 C. trachomatis reference strains. CT153 underwent a rapid infection-dependent proteolytic cleavage into polypeptides of 57 and 41 kDa that was independent of de novo chlamydial protein synthesis. Following productive infection, p91 was expressed during the mid-developmental cycle and was similarly processed into p57 and p41 fragments. Infected-cell fractionation studies showed that insoluble fractions contained p91, p57, and p41, whereas only p91 was found in the soluble fraction, indicating that unprocessed CT153 may be secreted. Finally, CT153 localized to a distinct population of reticulate bodies, some of which were in contact with the inclusion membrane.
Insights
Chlamydia trachomatis protein CT153, found in elementary bodies, is cleaved during infection. This protein localizes to distinct developmental forms within host cells, offering insights into chlamydial pathogenesis.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogen-Host Interactions
Background:
- Chlamydia trachomatis strains exhibit varied organotropisms despite genomic similarity.
- The chlamydial plasticity zone (PZ) is linked to pathogen-host relationship differences.
- Functions of PZ-encoded proteins like CT153 and pzPLDs remain largely unknown.
Purpose of the Study:
- To investigate the function and localization of the CT153 protein in Chlamydia trachomatis.
- To understand the processing and cellular location of CT153 during the chlamydial developmental cycle.
Main Methods:
- Detection of full-length CT153 (p91) in elementary bodies (EBs) across 15 reference strains.
- Analysis of CT153 proteolytic cleavage during infection, independent of de novo synthesis.
- Infected-cell fractionation to determine the localization of CT153 fragments.
- Microscopic localization of CT153 within infected host cells.
Main Results:
- Full-length CT153 (p91) is present in C. trachomatis EBs and processed into p57 and p41 fragments post-infection.
- Proteolytic cleavage of CT153 occurs rapidly after infection and is independent of new chlamydial protein synthesis.
- CT153 fragments are found in insoluble cellular fractions, while unprocessed p91 is in the soluble fraction.
- CT153 localizes to specific reticulate bodies, some interacting with the inclusion membrane.
Conclusions:
- CT153 is an infection-dependent protein processed within Chlamydia trachomatis.
- The localization and processing of CT153 suggest a role in membrane modification or interaction during infection.
- Unprocessed CT153 may be secreted, and its association with reticulate bodies indicates involvement in the chlamydial developmental cycle.
