Primary structure and function of a cytotoxic outer-membrane protein (ComP) of Plesiomonas shigelloides

We previously isolated and characterized a 40-kDa cytotoxic outer-membrane protein (ComP) produced by Plesiomonas shigelloides strain P-1 (P-1). Sequence analysis of the comP gene revealed a coding region of 1068 bp, with a predicted mature protein composed of 335 amino acids and a molecular mass of 38.597 kDa. Three-dimensional structural modeling of ComP suggests that it has a beta-barrel structure with 16 transmembrane strands, eight short periplasmic turns and eight external loops. blast search results and protein modeling suggest that ComP may be a novel porin protein of P. shigelloides. In order to understand the role of ComP during P. shigelloides infection, we constructed a deletion mutant strain (P. shigelloides DeltacomP; P-1201), and compared the pathogenicity of P-1201 vs. the wild-type strain P-1 in Caco-2 cells. Unlike P-1, the deletion strain P-1201 was not cytotoxic to Caco-2 cells and did not lead to apoptosis. These data indicate that ComP may be the predominant virulence factor that triggers cell death in the host cells following infection.