Protein Family Models

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, modeled 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:

2024-08-14

The FCT and equivalent region genes of Streptococcus pyogenes and other related bacteria encode surface proteins that include fibronectin- and collagen-binding proteins and the serological markers known as T antigens. Some of these proteins give rise to pilus-like appendages [1]. The FctA family is found in many Firmicutes and related bacteria. In S. pyogenes, the pili have a role in bacterial adherence and colonisation of human tissues [2]. Members of this family have a conserved N-terminal lysine and C-terminal asparagine that can form a covalent isopeptide bond [3]. [1]. 17012387. Role of streptococcal T antigens in superficial skin infection.. Lizano S, Luo F, Bessen DE;. J Bacteriol. 2007;189:1426-1434.. [2]. 17501921. Streptococcus pyogenes pili promote pharyngeal cell adhesion and. biofilm formation.. Manetti AG, Zingaretti C, Falugi F, Capo S, Bombaci M, Bagnoli. F, Gambellini G, Bensi G, Mora M, Edwards AM, Musser JM, Graviss. EA, Telford JL, Grandi G, Margarit I;. Mol Microbiol. 2007;64:968-983.. [3]. 18063798. Stabilizing isopeptide bonds revealed in gram-positive bacterial. pilus structure.. Kang HJ, Coulibaly F, Clow F, Proft T, Baker EN;. Science. 2007;318:1625-1628. (from Pfam)

Date:

2024-08-14

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

This HMM describes a domain that occurs once in the major pilin of Streptococcus pyogenes, Spy0128, but in higher copy numbers in other streptococcal proteins. The domain occurs nine times in a surface-anchored protein of Bifidobacterium longum. All members of this family have LPXTG-type sortase target sequences. The S. pyogenes major pilin has been shown to undergo isopeptide bond cross-linking, mediated by sortases, that are critical to maintaining pilus structural integrity. One such Lys-to-Asn isopeptide bond is to a near-invariant Asn near the C-terminal end of this domain (column 81 of the seed alignment). A Glu in the S. pyogenes major pilin (column 25 of the seed alignment), invariant as Glu or Gln, is described as catalytic for isopeptide bond formation.

Date:

2021-04-27