8,A.229.  The Chlamydial Inclusion Membrane Protein, MrcA (MrcA) Family 

The obligate intracellular bacterium, Chlamydia trachomatis, replicates within a parasitophorous vacuole termed an inclusion. During development, host proteins critical for regulating intracellular calcium (Ca2+) homeostasis interact with the inclusion membrane. The inclusion membrane protein, MrcA, interacts with the inositol-trisphosphate receptor (IP3R), an ER cationic channel that conducts Ca2+. Stromal interaction molecule 1 (STIM1), an ER transmembrane protein important for regulating store-operated Ca2+ entry (SOCE), localizes to the inclusion membrane via an uncharacterized interaction. Chamberlain et al. 2022 examined Ca2+ mobilization in C. trachomatis infected cells. Utilizing a variety of Ca2+ indicators to assess changes in cytosolic Ca2+ concentration, they demonstrate that C. trachomatis impairs host cell SOCE. Ca2+ regulates many cellular signaling pathways. The SOCE-dependent NFAT/calcineurin signaling pathway is impaired in C. trachomatis infected HeLa cells and likely has major implications on host cell physiology as it relates to C. trachomatis pathogenesis.



Chamberlain, N.B., Z. Dimond, and T. Hackstadt. (2022). Chlamydia trachomatis suppresses host cell store-operated Ca entry and inhibits NFAT/calcineurin signaling. Sci Rep 12: 21406.


TC#NameOrganismal TypeExample

Penicillin binding protein, MrcA of 428 aas and 1 - 3 TMSs.  This inclusion membrane protein interacts with the inositol trisphosphate receptor (IP3R) (TC# 1.A.3.2.6) influencing Ca2+ fluxes between the ER and the cytoplasm (Chamberlain et al. 2022).

MrcA of Chlamydia trachomatis


Membrane peptidoglycan carboxypeptidase of 847 aas and 1 N-terminal TMS.

PCP of Streptomyces avidinii