Staphylococcus aureus produces and secretes a small, basic protein, designated Efb, that binds to fibrinogen and seems to be required for virulence of the organism. A 3D model of Efb was developed, and it predicts that the C-terminal half of the protein contains substantial alpha-helical content. CD analysis of Efb yielded a value of 40-41% alpha-helix. Calcium and zinc both influence the interactions between Efb and fibrinogen, and an analysis of the amino acid sequence of Efb revealed the presence of consensus sequences for the binding of both metals.