The surface of Aeromonas salmonicida is covered by a tetragonal paracrystalline array (A-layer) composed of a single protein (A-protein, M(r)=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 K(d) = 1.52 nM), whereas fibronectin bound via two classes of interactions, one being similar to that of laminin (cell Class 2 interaction K(d) = 6.6 nM). This interaction with both proteins was partly hydrophobic. The Class 1 fibronectin interaction was of lower affinity (cell K(d) = 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.
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - Jan 1 1992|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology