Sequence, Structure, and Epitope Analysis of the Polymorphic Membrane Protein Family in Chlamydia trachomatis

The polymorphic membrane proteins are a family of autotransporters that play an important role in infection, adhesion and immunity in Chlamydia trachomatis. Here we show that the characteristic GGA(I,L,V) and FxxN tetrapeptide repeats fit into a larger repeat sequence, and that these repeats correspond to the coils of a large beta-helical domain in high quality structure predictions. While the tetranucleotide motifs themselves are predicted to play a structural role in folding and close stacking of the beta-helical backbone of the passenger domain, we found many of the interesting features of Pmps are localized to the side loops jutting out from the beta helix - including protease cleavage, host cell adhesion, and B-cell epitopes; while T-cell epitopes are predominantly found in the beta-helix itself.