ISOLATION AND SEQUENCE OF A CDNA CODING FOR THE IMMUNOGLOBULIN MU CHAIN OF THE SHEEP

A sheep cDNA library was screened with a human C-mu probe, and the complete nucleotide sequence of a 1923 nt cDNA was determined. It contains sequences corresponding to all the exons (V(H), D(H), J(H), C(H)1, C(H)2, C(H)3 and C(H)4) characteristic of the immunoglobulin-mu heavy chain regions. The deduced amino acid sequence shows a percentage of identical residues in the range 65-45% when compared with the mu-chains of various species. The V(H) region of this clone is clearly related to a group of genes that includes mouse V(H)36-60 and V(H)Q52, human V(H)2, V(H)4 and V(H)6 gene families and Xenopus V(H)II gene families. The constant region shows an unusual repartition of cystein and proline residues at the beginning of the C(H)2 domain, that may result in a molecule with enhanced stability and reduced flexibility.