SEQUENCE OF A 2ND GENE ENCODING BOVINE SUBMAXILLARY MUCIN - IMPLICATION FOR MUCIN HETEROGENEITY AND CLONING

Secreted epithelial mucins are extremely large and heterogeneous glyco proteins. me report the 5 kilobase DNA sequence of a second gene, BSM2 , which encodes bovine submaxillary mucin. The determined nucleotide a nd deduced amino acid sequences of BSM2 are 95.2% and 92.2% identical, respectively, to those of the previously described BSM1 gene isolated hom the same cow. Further, the five predicted protein domains of the two genes are 100%, 94%, 93%, 77%, and 88% identical. Based on the abo ve results, we propose that expression of multiple homologous core pro teins from a single animal is a factor in generating diversity of sacc harides in mucins and in providing resistance of the molecules to prot eolysis. In addition, this work raises several important issues in muc in cloning such as assembling sequences from seemingly overlapping clo nes and deducing consensus sequences for nearly identical tandem repea ts. (C) 1998 Academic Press.