The multifunctional fibrillar adhesin CshA, which mediates binding to both host molecules and other microorganisms, is an important determinant of colonization by Streptococcus gordonii, an oral commensal and opportunistic pathogen of animals and humans. CshA binds the high-molecular-weight glycoprotein fibronectin (Fn) via an N-terminal non-repetitive region, and this protein-protein interaction has been proposed to promote S. gordonii colonization at multiple sites within the host. This 259-kDa polypeptide is organized in the form of a leader peptide (residues 1-41), a non-repetitive region (residues 42-778), 17 repeat domains (R1-R17, each about 101-aa residues), and a C-terminal cell wall anchor. The non-repetitive Fn-binding region of CshA in turn is composed of three distinct domains, designated as non-repetitive domain 1 (NR1, CshA(42-222)), non-repetitive domain 2 (NR2, CshA(223-540)), and non-repetitive domain 3 (NR3, CshA(582-814)). The NR2 domain of CshA is shown to adopt a globular structure with a lectin-like fold and a ligand-binding site on its surface with structural homologues identified as those involved in binding carbohydrates or glycoproteins [1].

1: The Streptococcus gordonii Adhesin CshA Protein Binds Host Fibronectin via a Catch-Clamp Mechanism. Back CR, Sztukowska MN, Till M, Lamont RJ, Jenkinson HF, Nobbs AH, Race PR; J Biol Chem. 2017;292:1538-1549. PMID:27920201