Role of fibronectin-binding MSCRAMMs in bacterial adherence and entry intomammalian cells

Most bacterial infections are initiated by the adherence of microorganisms to host tissues. This process involves the interaction of specific bacteria l surface structures, called adhesins, with host components. In this review , we discuss a group of microbial adhesins known as Microbial Surface Compo nents Recognizing Adhesive Matrix Molecules (MSCRAMMs) which recognize and bind FN, The interaction of bacteria with FN is believed to contribute sign ificantly to the virulence of a number of microorganisms, including staphyl ococci and streptococci. Several FN-binding MSCRAMMs of staphylococci and s treptococci exhibit a similar structural organization and mechanism of liga nd recognition. The ligand-binding domain consists of tandem repeats of a s imilar to 45 amino acid long unit which bind to the 29-kDa N-terminal regio n of FN. The binding mechanism is unusual in that the repeat units are unst ructured and appear to undergo a conformational change upon ligand binding. Apart from supporting bacterial adherence, FN is also involved in bacteria l entry into non-phagocytic mammalian cells. A sandwich model has been prop osed in which FN forms a molecular bridge between MSCRAMMs on the bacterial surface and integrins on the host cell, However, the precise mechanism of bacterial invasion and the roles of FN and integrins in this process have y et to be fully elucidated. (C) 1999 Elsevier Science B.V./International Soc iety of Matrix Biology. All rights reserved.