The present study reports on fibrinogen (Fg) binding of Staphylococcus epidermidis . Adhesion of different S. epidermidis strains to immobilized Fg was found to vary significantly between different strains, and the component responsible was found to be proteinaceous in nature. To further characterize the Fg-binding activity, a shotgun phage display library covering the S. epidermidis chromosome was constructed. By affinity selection (panning) against immobilized Fg, a phagemid clone, pSEFG1, was isolated, which harbors an insert with an open reading frame of ∼1.7 kilobases. Results from binding and inhibition experiments demonstrated that the insert of pSEFG1 encodes a specific Fg-binding protein. Furthermore, affinity-purified protein encoded by pSEFG1 completely inhibited adhesion of S. epidermidis to immobilized Fg. By additional cloning and DNA sequence analyses, the complete gene, termed fbe , was found to consist of an open reading frame of 3,276 nucleotides encoding a protein, called Fbe, with a deduced molecular mass of ∼119 kDa. With a second phage display library made from another clinical isolate of S. epidermidis , it was possible to localize the Fg-binding region to a 331-amino-acid-long fragment. PCR analysis showed that the fbe gene was found in 40 of 43 clinical isolates of S. epidermidis . The overall organization of Fbe resembles those of other extracellular surface proteins of staphylococci and streptococci. Sequence comparisons with earlier known proteins revealed that this protein is related to an Fg-binding protein of Staphylococcus aureus called clumping factor.

The gene for protein A from Staphylococcus aureus was cloned into pBR322 in Escherichia coli. An immunoassay was used to detect production of the protein. Protein A produced in E. coli was found in the periplasmic space and was purified and concentrated by IgG-Sepharose affinity chromatography. DNA sequence assay of the gene revealed a region with the general features of a prokaryotic signal peptide and a fifth structural region homologous to the four repetitive regions found earlier by amino acid sequence determination of the mature protein. Upstream from the structural gene there is a possible promoter region and a ribosomal binding sequence typical of gram-positive bacteria. The initiation codon is TTG.

The complete sequence of the structural gene encoding the immunoglobulin G binding protein from Streptococcus G148 has been determined, as well as its 5′ and 3′ flanking sequences. The sequence reveals an open reading frame encoding a putative preprotein with a relative molecular mass of 63294. N-Terminal sequencing of the mature protein, spontaneously released from streptococcal cells, demonstrates that the signal peptide consists of 33 amino acids. The DNA sequence reveals extensive internal homologies similar to other cell-wall-bound receptors from gram-positive bacteria. Comparisons with a related gene previously isolated from another strain of streptococci revealed large differences in size, due to variations in the number of internal repeats. The structure of the gene suggests an evolution through multiple duplications.