CLONING AND SEQUENCING OF BES-1 GENE ENCODING THE IMMUNOGENIC ANTIGENOF STREPTOCOCCUS-SANGUIS KTH-1 ISOLATED FROM THE PATIENTS WITH BEHCETS-DISEASE

In order to analyze the immunopathologic mechanisms of Behcet's diseas e, the gene (bes-l) encoding a streptococcal antigen correlated with t he disease was cloned and sequenced, and protein produced by this clon e was identified by Western immunoblotting using serum antibody from t he patient. Cellular DNA of Streptococcus (S.) sanguis serotype KTH-1 (uncommon serotype 1, strain 113-20) from the patient was extracted an d digested with EcoRI. The digested fragments were cloned into the clo ning vector lambda gt11, and then the resulting DNA library was immuno screened using the patient's serum antibody to serotype KTH-1. The imm unopositive clone of the 1.5 kbp fragment was subcloned into pUC 118 p lasmid (pU8BeS1-1) and sequenced. The sequence showed that the 3'-term inal half side region of this insert contained 962bp of open-reading f rame (ORF) discontinued at the EcoRI restriction site, and the stop co don was not found. The nucleotide sequence of the remaining additional 3'-terminal region of this gene encoding whole BES-1 was determined b y genome walking. The whole ORF of bes-l consisted of 849 amino acid r esidues with a calculated molecular mass of 95 kDa. The residues in a portion of the amino acid sequence showed a 60% correspondence to thos e of the human intraocular peptide Brn-3b.