spa
Domain
Each of the immunoglobulin-binding region repeats can bind the Fc region of an immunoglobulin (PubMed:2938951). Cell wall anchoring is conferred by the LPXTG motif and following sequences (residues 482-516) which are necessary and sufficient to target other proteins to the cell wall (PubMed:1638631). The YSIRK-G/S motif in the signal sequence plays a role in the secretion efficiency for SpA, it may have a specialized recognition mode (Probable).
Function
Plays a role in the inhibition of the host innate and adaptive immune responses. Possesses five immunoglobulin-binding domains that capture both the fragment crystallizable region (Fc region) and the Fab region (part of Ig that identifies antigen) of immunoglobulins (PubMed:10805799, PubMed:2938951, PubMed:4163007). In turn, Staphylococcus aureus is protected from phagocytic killing via inhibition of Ig Fc region. In addition, the host elicited B-cell response is prevented due to a decrease of antibody-secreting cell proliferation that enter the bone marrow, thereby decreasing long-term antibody production. Inhibits osteogenesis by preventing osteoblast proliferation and expression of alkaline phosphatase, type I collagen, osteopontin and osteocalcin. Acts directly as a pro-inflammatory factor in the lung through its ability to bind and activate tumor necrosis factor alpha receptor 1/TNFRSF1A (By similarity).
Sequence Similarities
Belongs to the immunoglobulin-binding protein SpA family.
Cellular localization
- Secreted
- Cell wall
- Peptidoglycan-anchor
- Extracellular side
- Secreted
- Cell wall anchoring is conferred by the LPXTG motif and following sequences (PubMed:1638631). Anchored by sortase A (PubMed:10427003). SpA from strains A676 and V-I is secreted whereas SpA from Cowan 1 and 8325-4 is mostly attached to the cell wall (Probable). Newly synthesized protein is deposited at 2-4 foci/cell and eventually is distributed in a ring around the cell (PubMed:17416657).
Alternative names
SAOUHSC_00069, spa, Immunoglobulin G-binding protein A, IgG-binding protein A, Staphylococcal protein A, SpA