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' translated 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%).