Protein Family Models

Many surface proteins found in Streptococcus, Staphylococcus, and related lineages share apparently homologous signal sequences. A motif resembling [YF]SIRKxxxGxxS[VIA] appears at the start of the transmembrane domain. The GxxS motif appears perfectly conserved, suggesting a specific function and not just homology. There is a strong correlation between proteins carrying this region at the N-terminus and those carrying the Gram-positive anchor domain with the LPXTG sortase processing site at the C-terminus. (from Pfam)

Date:

2023-12-12

This short repeat is found in multiple copies in bacterial M proteins. The M proteins bind to IgA and are closely associated with virulence. The M protein has been postulated to be a major group A Streptococcal (GAS) virulence factor because of its contribution to the bacterial resistance to opsonophagocytosis [1]. [1]. 8830235. M-related protein (Mrp) contributes to group A streptococcal. resistance to phagocytosis by human granulocytes.. Podbielski A, Schnitzler N, Beyhs P, Boyle MD;. Mol Microbiol 1996;19:429-441. (from Pfam)

Date:

2024-04-03

Date:

2023-12-12

This model describes the LPXTG motif-containing region found at the C-terminus of many surface proteins of Streptococcus and Streptomyces species. Cleavage between the Thr and Gly by sortase or a related enzyme leads to covalent anchoring at the new C-terminal Thr to the cell wall. Hits that do not lie at the C-terminus or are not found in Gram-positive bacteria are probably false-positive. A common feature of this proteins containing this domain appears to be a high proportion of charged and zwitterionic residues immediatedly upstream of the LPXTG motif. This model differs from other descriptions of the LPXTG region by including a portion of that upstream charged region.

Date:

2021-04-27

The [YF]SIRKxxxGxxS type of signal peptide appears at the start of many proteins of Streptococcus, Staphylococcus, and Enterococcus, but not in other lineages such as Bacillus. Recent work in Staphylococcus aureus has shown that septal secretion (targeting to the crosswall in dividing cells) of the YSIRK-containing staphylococcal protein A depends on SecA, SecDF, and the lipoteichoic acid synthase LtaS, all of which co-purify when the motif is modified to YSIRKxxxGxxL to block processing.

Date:

2019-12-09

M protein (emm) is an important virulence protein and serology-defining surface antigen of Streptococcus pyogenes (group A Streptococcus). M protein has an amino-terminal YSIRK-type signal sequence (associated with cross-wall targeting in dividing cells), and a C-terminal LPXTG domain for processing by sortase and covalent attachment to the Gram-positive cell wall. Past the signal peptide, M protein has a hypervariable region, but this HMM describes only the well-conserved region C-terminal to the hypervariable region. It discriminates M protein from two related proteins, Enn and Mrp.

Gene:

emm

Date:

2020-10-26