Peptide Sequence Region That Is Essential for the Interactions of the Enterotoxigenic Bacteroides Fragilis Metalloproteinase II With E-Cadherin
Sergey A. Shiryaev, Albert G. Remacle, Piotr Cieplak, Alex Y Strongin
Abstract
Bacteroides fragilis is a valuable anaerobic commensal and an essential component of the gut microbiome in humans. The presence of a short pathogenicity island in the genome is predominantly associated with the enterotoxigenic strains of B. fragilis. Metalloproteinase II (MPII) and fragilysin (FRA) are the structurally related enzymes encoded by the pathogenicity island in the enterotoxigenic strains. Accordingly, there is a significant overlap between the cleavage preferences of MPII and FRA. These proteinases, however, are counter-transcribed in the bacterial genome suggesting their distinct and specialized functions in the course of infection. It is well established that FRA directly cleaves E-cadherin, a key protein of the cell-to-cell adhesion junctions in the intestinal epithelium. Counterintuitively, MPII directly binds to, rather than cleaves, E-cadherin. Structural modeling suggested that a potential E-cadherin binding site involves the C-terminal α-helical region of the MPII catalytic domain. The sequence of this region is different in MPII and FRA. Here, we employed substitution mutagenesis of this C-terminal α-helical region to isolate the MPII mutants with the potentially inactivated E-cadherin binding site. Overall, as a result of our modeling, mutagenesis and binding studies, we determined that the C-terminal ten residue segment is essential for the binding of MPII, but not of FRA3, to E-cadherin, and that the resulting MPII•E-cadherin complex does not impair E-cadherin-dependent cell-to-cell contacts. It is possible to envision that the putative cleavage targets of MPII should be explored not only on the host cell surface but also in B. fragilis.
J. Proteolysis Vol 1, No 1 (2014); doi:10.13176/14.618 | Full Text: PDF | Share this paper: