Genes encoding α-heavy chains of rabbit IgA: characterization of cDNA encoding IgA-g subclass α-chains

摘要

cDNA molecules encoding rabbit IgA α-heavy chains have been synthesized and six of these have been characterized. The complete nucleotide sequence of one cDNA, p 19 (942bp), showed that it encoded all but the N-terminal 57 amino acid residues of the constant region of α-chains. The cDNA molecules were subcloned into the expression vector pUC8 and E. coli were transformed. Radioimmunoassay of the molecules synthesized by these clones showed that all six cDNA molecules encoded α-chains of the IgA-g subclass. Comparison of the amino acids encoded by the α-cDNA with the amino acid sequence of mouse and human α-chains showed that although all of the intradomain disulfide bonds appear to be conserved, some positions, probably involved in interchain disulfide bonds, are not conserved. We propose that secretory component is covalently bound to cystelne 299 and/or cystelne 301 of the CH2 domain of mouse and human α-chains. The results from Southern blot analysis of genomic DNA with 32P-cDNA suggests that the rabbit genome has multiple Cα genes.