9.B.184 The Putative Spirochaete Outer Membrane Omp-like Porin (Sp-Omp) Family
When the T. pallidum Nichols strain genome was initially annotated, the TP0126 open reading frame was predicted to include a poly-G tract, and did not appear to have a predicted signal sequence that might suggest the possibility of its being an OMP. Giacani et al. 2015 showed that the initial annotation was incorrect, that this poly-G is instead located within the TP0126 promoter, and that it varies in length in vivo during experimental syphilis. They further showed that TP0126 transcription is affected by changes in the poly-G length consistent with regulation by phase variation. In silico analysis of the TP0126 open reading frame based on the experimentally identified transcriptional start site shortened this hypothetical protein by 69 amino acids, revealed a predicted cleavable signal peptide, and suggested structural homology with the OmpW family of porins. Circu Circuchroism of recombinant TP0126 supported structural homology to OmpW. Together with the evidence that TP0126 is fully conserved among T. pallidum subspecies and strains, these data suggest an important role for TP0126 in T. pallidum biology and syphilis pathogenesis.