Cloning and sequence analysis of bovine corneal antigen (coag) cdna: identification of host-parasite protein calgranulin c

Purpose. A cornea-associated antigen (CO-Ag) has been implicated in the pathogenesis of Mooren's ulcer. The study design was to isolate a full-length clone encoding CO-Ag from a bovine corneal cDNA library so that a complete sequence analysis might further define the possible role of this protein in Mooren's ulcer. Methods. A DNA fragment of CO-Ag was generated using unique oligonucleotide primers and reverse transcription polymerase chain reaction. This fragment was used as a probe to obtain cDNA clones from a bovine corneal cDNA library. Results. The cDNA insert sequence was 273 nucleotides in length for the entire mRNA coding region, 212 nucleotides in the 5' untranslated region, 83 nucleotides in the 3' untranslated region and a poly(A) tail. The DNA base sequence of this clone also contained a standard initiation codon, termination codon, and the polyadenylation signal. This cDNA predicts a protein which contains 91 amino acids with a molecular weight of 10,584 daltons. The cDNA and deduced amino acid sequence of CO-Ag are completely identical to a S-100 protein, bovine calgranulin C, whose human counterpart has been isolated from neutrophils and has been isolated on the surface of filarial nematodes. Conclusions. We report the isolation and analysis of a cDNA clone containing the complete coding sequence of the CO-Ag protein, the protein identification by deduced amino acid sequence, and the possible relationship of CO-Ag in a hostparasite interaction in the etiology of Mooren's ulcer.