Proteome-scale identification of outer membrane proteins in Mycobacterium avium subspecies paratuberculosis using a structure based combined hierarchical approach.

Outer membrane proteins (OMPs) in eubacteria have several important roles, which range from membrane transport to the host-pathogen interactions. These are directly involved in pathogen attachment, entry and activation of several pathogen-induced signaling cascades in the cell. The cardinal structural features of OMPs include the presence of a β-barrel, a signal peptide and the absence of the transmembrane helix. This is the first report on proteome-wide identification of OMPs of ruminant pathogen, Mycobacterium avium subsp. paratuberculosis (MAP). The complete proteome of MAP was analyzed using a pipeline of algorithms, which screens the amino acid sequences and structural features shared by OMPs in other bacteria. Secondary structure of these proteins is also analyzed and scores are calculated for amphiphilic β-strands. From the set of 588 exported proteins, 264 proteins are predicted to be inner membrane proteins while 83 proteins are identified as potential OMPs in MAP. Finally, this study identified 57 proteins as top candidates, on the basis of computed isoelectric points, as the core set of OMPs. Significantly, the resulting data for OMPs are not only useful in designing novel vaccines but may also open avenues for the development of early serodiagnostic tools for MAP.