1.B.38.1.4
Major outer membrane sheath protein, Msp or MOSP, of 543 aas.  Msp has a bipartide structure and exists as periplasmic and outer membrane-integrated trimeric conformers (Anand et al. 2013).  The N-terminal domain (residues 77 - 286) does not insert into the membrane, but the C-terminal domain (residues 332 - 543) does to form pores (Anand et al. 2013).  It resembles the surface exposed variable antigen, TprK (Giacani et al. 2012) which plays roles in immune evasion and persistence.  MOSP is one of its principal cell surface virulence determinants. Bioinformatics predicts that MOSP consists of N- and C-terminal domains, MOSP^N and MOSP^C. Biophysical analysis of constructs refolded in vitro demonstrated that MOSP^C, which has porin activity, forms amphiphilic trimers, while MOSP^N forms an extended hydrophilic monomer (Puthenveetil et al. 2017). It is a also a pore-forming cytotoxin that inserts into animal cell membranes (see TC# 1.C.128.1.1), and is a constituent of the outer membrane lipoprotein-protease complex of the Dentilisin Family (TC# 9.B.355).