title: Binding of laminin and fibronectin by the trypsin-resistant major structural domain of the crystalline virulence surface array protein of Aeromonas salmonicida.
abstract: The surface of Aeromonas salmonicida is covered by a tetragonal paracrystalline array (A-layer) composed of a single protein (A-protein, Mr = 50,778). This array is a virulence factor. Cells containing A-layer and isolated A-layer sheets specifically bound laminin and fibronectin with high affinity. Binding by cells was inactivated by selective removal of A-layer at pH 2.2, and neither isogenic A-layer-deficient A. salmonicida mutants nor tetragonal paracrystalline array producing Aeromonas hydrophila and Aeromonas sobria strains bound either matrix protein. Laminin binding was by a single class of high affinity interactions (cell Kd = 1.52 nM), whereas fibronectin bound via two classes of interactions, one being similar to that of laminin (cell Class 2 interaction Kd = 6.6 nM). This interaction with both proteins was partly hydrophobic. The Class 1 fibronectin interaction was of lower affinity (cell Kd = 218 nM) and distinct. Purified A-protein inhibited binding of both matrix proteins to A-layer, and trypsin cleavage localized the matrix-protein binding region to the N-terminal major trypsin-resistant structural domain of A-protein. Monoclonal antibody inhibition studies showed that A-protein was folded such that Fabs of only one of two antibodies with epitopes mapping C-terminal to this trypsin-resistant peptide was capable of blocking binding.
authors.affiliation: Department of Biochemistry, University of Victoria, British Columbia, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Doig
authors.forename: L
authors.initials: L
authors.lastname: Emödy
authors.forename: T J
authors.initials: TJ
authors.lastname: Trust
mesh_terms: D000333:Aeromonas / Q000378:metabolism*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D003460:Crystallization; D005353:Fibronectins / Q000378:metabolism*; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D007797:Laminin / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009994:Osmolar Concentration; D012965:Sodium Chloride; D013379:Substrate Specificity; D014357:Trypsin / Q000378:metabolism; D037521:Virulence Factors
chemical_list: D001426:Bacterial Proteins; D005353:Fibronectins; D007797:Laminin; D008562:Membrane Glycoproteins; D037521:Virulence Factors; D012965:Sodium Chloride; D014357:Trypsin