Complete nucleotide sequence of HLA-B*0703, a B7 variant (BPOT).

HLA-B703 (BPOT) is a B7-like antigen segregating within families. To determine the complete B*0703 nucleotide sequence, HLA-ABC-cDNAs derived from the EBV cell line POT71 have been cloned. Four B*0703-positive clones were sequenced to obtain an accurate consensus sequence. With respect to the isoelectric focusing-identical HLA-B*0702 allelic product, HLA-B*0703 differed only in a cluster of four nucleotide substitutions in exon 2 and a single (silent) nucleotide substitution in exon 3. The resulting amino acid substitutions in the alpha 1 domain of B703 at residues 69 (Ala-->Thr), 70 (Gln-->Asn), and 71 (Ala-->Thr) probably have their origin in a segmental exchange between B7 and other B alleles.