title: Characterization of CPAF critical residues and secretion during Chlamydia trachomatis infection.
abstract: CPAF (chlamydial protease-like activity factor), a Chlamydia serine protease, is activated via proximity-induced intermolecular dimerization that triggers processing and removal of an inhibitory peptide occupying the CPAF substrate-binding groove. An active CPAF is a homodimer of two identical intramolecular heterodimers, each consisting of 29-kDa N-terminal and 35-kDa C-terminal fragments. However, critical residues for CPAF intermolecular dimerization, catalytic activity, and processing were defined in cell-free systems. Complementation of a CPAF-deficient chlamydial organism with a plasmid-encoded CPAF has enabled us to characterize CPAF during infection. The transformants expressing CPAF mutated at intermolecular dimerization, catalytic, or cleavage residues still produced active CPAF, although at a lower efficiency, indicating that CPAF can tolerate more mutations inside Chlamydia-infected cells than in cell-free systems. Only by simultaneously mutating both intermolecular dimerization and catalytic residues was CPAF activation completely blocked during infection, both indicating the importance of the critical residues identified in the cell-free systems and exploring the limit of CPAF's tolerance for mutations in the intracellular environment. We further found that active CPAF was always detected in the host cell cytoplasm while nonactive CPAF was restricted to within the chlamydial inclusions, regardless of how the infected cell samples were treated. Thus, CPAF translocation into the host cell cytoplasm correlates with CPAF enzymatic activity and is not altered by sample treatment conditions. These observations have provided new evidence for CPAF activation and translocation, which should encourage continued investigation of CPAF in chlamydial pathogenesis.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Zhangsheng
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA Department of Clinic Laboratory, 2nd Xiangya Hospital, Central South University, Changsha, Hunan, People's Republic of China.
authors.forename: Lingli
authors.initials: L
authors.lastname: Tang
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA Department of Obstetrics and Gynecology, 3rd Xiangya Hospital, Central South University, Changsha, Hunan, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing, People's Republic of China.
authors.forename: Jijie
authors.initials: J
authors.lastname: Chai
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA Zhongg@UTHSCSA.edu.
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhong
mesh_terms: D000595:Amino Acid Sequence; D002690:Chlamydia Infections / Q000382:microbiology*; D002692:Chlamydia trachomatis / Q000378:metabolism*; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D009154:Mutation
chemical_list: D010450:Endopeptidases; C425923:CPA factor