Molecular characteristics of the SLA-2 gene from Chinese Hebao pigs

Abstract

To study the molecular characteristics of swine leukocyte antigen (SLA) class I from the Hebao pig, a rare inbreed in China, a pair of primers was designed to amplify the SLA 2 gene (SLA 2 HB) and then the molecular characteristics of the gene were analyzed by computer. After cloning, sequencing and computer analysis, four SLA 2 HB alleles were found, all of 1119 bp. Sites 3-1097 were an open reading frame encod ing 364 amino acids with two sets of intra chain disulfide bonds comprising four cysteines situated in sites 125, 188, 227 and 283. By alignment of SLA 2 HB sequences with other SLA 2 alleles in the DNA Data Bank of Japan/European Molecular Biology Laboratory/GenBank database, nine key variable amino acid sites were found in the extracellular domain of the SLA 2 HB alleles at sites 23(F), 24(I), 43(A), 44(K), 50(Q), 73(N), 95(I), 114(R) and 216(S), which could be used to differentiate other SLA 2 alleles. The amino acid identities between SLA 2 HB and other SLA 2, SLA 3 and SLA 1 alleles were 87.1-97.0%, 85.0-93.9% and 83.3-88.6%, respectively. The phylogenetic tree of SLA 2 HB showed that it was relatively independent of the other SLA 2 genes. Furthermore, the SLA 2 HB alleles were similar to HLA B15 and HLA A2 functional domains and preserved some functional sites of HLA A2. It was concluded that SLA 2 HB is an allele of SLA 2 and that the Hebao pig might have evolved independently in China.