CHARACTERIZATION OF A CDNA CLONE ENCODING FOR A PORCINE IMMUNOGLOBULIN MU-CHAIN

We present the complete sequence of cDNA clone BLM6, isolated from a porcine spleen cDNA library. BLM6 encodes for the constant region of a secreted mu-heavy chain. The cDNA is 1342 bp in length, begins within C-mu-1, and terminates in the 3' untranslated region. The deduced amino acid sequence indicates there are 111 amino acids in C-mu-2, 106 in C-mu-3, and 113 in C-mu-4, along with 19 carboxy-terminal residues that comprise the secreted terminus. The full length transcript is approximately 2.4 kb as determined by Northern blot analysis. Southern blot analysis suggests there is only one mu-chain gene within the porcine genome. Comparison of the deduced amino acid sequence of porcine C-mu with other mammalian C-mu sequences indicates that the overall identity is approximately 60%, with the greatest identity seen in the secreted terminus (approximately 85%) and C-mu-4 (approximately 70%); and less identity in C-mu-3 (60%) and C-mu-2 (50%).