Further biochemical characterization of Mycobacterium leprae laminin-binding proteins

It has been demonstrated that the alpha2 chain of laminin-2 present on the surface of Schwann cells is involved in the process of attachment of;Mycoba cterium leprae to these cells. Searching for M. leprae laminin-binding mole cules, in a previous study we isolated and characterized the cationic prote ins histone-like protein (Hlp) and ribosomal proteins S4 and S5 as potentia l adhesins involved in M. leprae-Schwann cell interaction. Hip was shown to bind alpha2-laminins and to greatly enhance the attachment of mycobacteria to ST88-14 Schwann cells. In the present study, we investigated the lamini n-binding capacity of the ribosomal proteins S4 and S5. The genes coding fo r these proteins were PCR amplified and their recombinant products were sho wn to bind alpha2-laminins in overlay assays. However, when tested in ELISA -based assays and in adhesion assays with ST88-14 cells, in contrast to Hip , S4 and S5 failed to bind laminin and act as adhesins, The laminin-binding property and adhesin capacity of two basic host-derived proteins were also tested, and only histones, but not cytochrome c, were able to increase bac terial attachment to ST88-14 cells. Our data suggest that the alanine/lysin e-rich sequences shared by Hip and eukaryotic H1 histones might be involved in the binding of these cationic proteins to laminin.