ABSTRACT

The Yersinia pestis Pla belongs to the omptin family of outer membrane proteases that have been detected in enterobacterial species pathogenic to humans or plants (Table 1). The name of the family is derived from the first well-characterized member, OmpT of Escherichia coli. The omptins are highly related in structure: they share about 50% sequence identity, their mature forms are 292-298 amino acid residues long, and

Bacterium Omptin Gene location Reference

Yersinia pestis Pla plasmid pPCP1 Sodeinde and Goguen, 1989

Salmonella enterica

PgtE chromosome Guina et al., 2000

Escherichia coli OmpT chromosome Grodberg et al., 1988

Escherichia coli OmpP F plasmid Matsuo et al., 1999

Shigella flexneri SopA virulence plasmid pWR100

Egile et al., 1997

Erwinia pyrifoliae Pla endopeptidase A

plasmid pEP36 McGhee et al., 2002

they lack or have a low content of cysteines. The omptin genes are located either on the chromosome or on a plasmid, which in Y. pestis and in Shigella flexneri is associated with virulence. OmpT has been crystallized and serves as the prototype of an omptin molecule. The structure of OmpT shows a 10-stranded antiparallel β-barrel that traverses the outer membrane and protrudes far from the outer membrane into the extracellular space (Vandeputte-Rutten et al., 2001). The OmpT β-barrel has five surface loops, which are located at the distance of about 40 Å from the outer membrane. The high sequence similarity of the omptins, as well as topology and structure modeling have led to the conclusion that the β-barrel structure is shared by the other omptin molecules as well. It is not presently known whether the omptins occur in the outer membrane as monomers or as polymeric complexes. For sequence comparison and structural data on the omptin family, the reader is referred to the MEROPS data base (https://merops.sanger.ac.uk/).