Extracellular fibrinogen-binding protein (Efb) (Efb)

Extracellular fibrinogen-binding protein (Efb) is a multifunctional secretable virulence factor produced by Staphylococcus aureus that facilitates immune evasion (UniProt P0C0L5). The protein is composed of two distinct functional domains: a disordered N-terminal domain that binds to host fibrinogen and a structured C-terminal domain (Efb-C) that targets complement component C3 (PMID: 15153530). By binding to the C3d thioester-containing domain of C3, Efb-C prevents the formation of C3 convertases and inhibits the opsonization and subsequent phagocytosis of the bacteria (PMID: 21930766). Furthermore, the N-terminal interaction with fibrinogen can inhibit platelet aggregation and form a protective protein shield around the pathogen, further shielding it from host defenses (PMID: 11544151). Given its pivotal role in neutralizing the innate immune system, Efb is a significant therapeutic target for adjunctive treatments against S. aureus infections, including methicillin-resistant S. aureus (MRSA). Therapeutic strategies under investigation include monoclonal antibodies designed to neutralize Efb's complement-inhibitory activity and restore host immune clearance (PMID: 24014883).

Other names

FibFibrinogen-binding proteinEfb-CComplement inhibitor Efb

Efb inhibits the host immune response by binding to the C3d domain of complement C3 to prevent the formation of C3 convertase and subsequent opsonization (PMID: 15153530). It also binds to host fibrinogen via its N-terminal domain, which can block platelet-fibrinogen interactions and create a protective protein shield around the bacteria to evade host clearance (PMID: 11544151).