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1.B.2 The Chlamydial Porin (CP) Family

The chlamydial major outer membrane porin, MomP or Omp1, functions to permit the diffusion of solutes through the intrareticular body membrane. It has 402 amino acyl residues and is believed to be disulfide-bonded to other outer membrane constituents. A homologue, PorB, which transports neutral solutes poorly, has been shown to transport dicarboxylates such as 2-ketoglutarate (Kubo and Stephens, 2001).

MOMP trimers are stable under reducing conditions, although disulfide bonds appear to be present between the monomers of a trimer and between trimers (Sun et al., 2007). Cross-linking of the outer membrane complex demonstrated that the MOMP is most likely not in a close spatial relationship with the 60- and 12-kDa cysteine-rich proteins. The trimers consist mainly of β-pleated sheet structures. Using a liposomal swelling assay, the MOMP was found to have porin activity, approximately 2 nm in diameter (Sun et al., 2007).

References associated with 1.B.2 family:

Atanu, F.O., E. Oviedo-Orta, and K.A. Watson. (2013). A Novel Transport Mechanism for MOMP in Chlamydophila pneumoniae and Its Putative Role in Immune-Therapy. PLoS One 8: e61139. 23637791
Jeanteur, D., J.H. Lakey, and F. Pattus. (1991). The bacterial porin superfamily: sequence alignment and structure prediction. Mol. Microbiol. 5: 2153-2164. 1662760
Jeanteur, D., J.H. Lakey, and F. Pattus. (1994). The porin superfamily: diversity and common features. In: Bacterial Cell Wall. Edited by Ghuysen, J.M., Hakenbeck, R. Elsevier, Amsterdam, pp. 363-380.
Kubo, A. and R.S. Stephens. (2000). Characterization and functional analysis of PorB, a Chlamydia porin and neutralizing target. Mol. Microbiol. 38: 772-780. 11115112
Kubo, A. and R.S. Stephens. (2001). Substrate-specific diffusion of select dicarboxylates through Chlamydia trachomatis PorB. Microbiology 147: 3135-3140. 11700364
Nikaido, H. (1992). Porins and specific channels of bacterial outer membranes. Mol. Microbiol. 6: 435-442. 1373213
O'Neill, C.E., H.M. Seth-Smith, B. Van Der Pol, S.R. Harris, N.R. Thomson, L.T. Cutcliffe, and I.N. Clarke. (2013). Chlamydia trachomatis clinical isolates identified as tetracycline resistant do not exhibit resistance in vitro: whole-genome sequencing reveals a mutation in porB but no evidence for tetracycline resistance genes. Microbiology 159: 748-756. 23378575
Pickett, M.A., M.E. Ward, and I.N. Clarke. (1988b). High-level expression and epitope localization of the major outer membrane protein of Chlamydia trachomatis serovar L1. Mol. Microbiol. 2: 681-685. 2460720
Pickett, M.A., S.J. Everson, and I.N. Clarke. (1988a). Chlamydia psittaci ewe abortion agent: complete nucleotide sequence of the major outer membrane protein gene. FEMS Microbiol. Lett. 55: 229-234.
Rodríguez-Marañón, M.J., R.M. Bush, E.M. Peterson, T. Schirmer, and L.M. de la Maza. (2002). Prediction of the membrane-spanning β-strands of the major outer membrane protein of Chlamydia. Protein. Sci. 11: 1854-1861. 12070338
Schulz, G.E. (1996). Porins: general to specific, native to engineered passive pores. Curr. Opin. Struc. Biol. 6: 485-490. 8794162
Sun, G., S. Pal, A.K. Sarcon, S. Kim, E. Sugawara, H. Nikaido, M.J. Cocco, E.M. Peterson, and L.M. de la Maza. (2007). Structural and Functional Analyses of the Major Outer Membrane Protein of Chlamydia trachomatis. J. Bacteriol. 189:6222-6235. 17601785