Protein Family Models

This repeated domain is found at the C-terminus of cell surface antigens [1-3]. In the Streptococcus mutans antigen I/II there are three repeats of this domain, a cleft between the first two of these forms a binding site for the human salivary agglutinin (SAG) [3]. [1]. 12485987. A novel variant of the immunoglobulin fold in surface adhesins of Staphylococcus aureus: crystal structure of the fibrinogen-binding MSCRAMM, clumping factor A. Deivanayagam CC, Wann ER, Chen W, Carson M, Rajashankar KR, Hook M, Narayana SV;. EMBO J. 2002;21:6660-6672. [2]. 20138058. Two intramolecular isopeptide bonds are identified in the crystal structure of the Streptococcus gordonii SspB C-terminal domain. Forsgren N, Lamont RJ, Persson K;. J Mol Biol. 2010;397:740-751. [3]. 21505225. Crystal structure of the C-terminal region of Streptococcus mutans antigen I/II and characterization of salivary agglutinin adherence domains. Larson MR, Rajashankar KR, Crowley PJ, Kelly C, Mitchell TJ, Brady LJ, Deivanayagam C;. J Biol Chem. 2011;286:21657-21666. (from Pfam)

Date:

2024-10-16

This is the second domain (C2) located in the C-terminal region found in antigen I/II type adhesin protein AspA from S. pyogenes. Together with C3, these two domains form an elongated structure, each domain adopts the DEv-IgG fold. Similar to the classical IgG folds, it is comprised of two major antiparallel beta-sheets, designated ABED and CFG. For the C2-domain, there are two additional strands on the CFG sheet. Furthermore, sheets ABED and CFG are interconnected by several cross-connecting loops and one alpha-helix (DH1). The side chains of D982 and N996 in the C2-domain are involved in hydrogen bonding with the side chains of R1264 and N1295 in the C3 domain. Main chain hydrogen bonding can also be observed between S992 in C2 and N1189/G1191 in C3, furthermore stabilizing the interaction between the domains. The C2 domain contains one bound metal ion, modelled as Ca2+, and both the C2- and C3-domains are stabilized by conserved isopeptide bonds, which connect the beta-sheets of the central DEv-IgG motifs [1].Other members of this family include Major cell-surface adhesin PAc from Streptococcus mutans and SspB from Streptococcus gordonii. [1]. 24918040. Structure of the C-terminal domain of AspA (antigen I/II-family) protein from Streptococcus pyogenes. Hall M, Nylander S, Jenkinson HF, Persson K;. FEBS Open Bio. 2014;4:283-289. (from Pfam)

Date:

2024-10-16

This domain has a conserved Lys (position 3 in seed alignment) and Asn at 177 that form an intramolecular isopeptide bond. The Asp (or Glu) at position 59, first position of the motif DDYDQ, forms hydrogen bonds to moieties in the isopeptide bond.

Date:

2023-11-14