1.B.38 The Treponema Porin Major Surface Protein (TP-MSP) Family

MSP is a 53 kDa (474 aa) surface antigen in the outer sheath of Treponema denticola. It is an adhesin, but additionally it has been purified to homogeneity and reconstituted in black lipid membranes where it showed channel activity (Egli et al., 1993). It also induces channel activity in HeLa cell membranes (Mathers et al., 1996). The channel had a single conductance of 1.8 nS in 0.1 M KCl (estimated pore diameter of 3.4 nm), the largest porin channel documented in 1996. Electron microscopy suggested a regular hexagonal array in the membrane. Homologues are found in other Treponema species.

The transport reaction catalyzed by MSP is:

ions (non-selective)(periplasm) ions (out)