Characterization of BF2 and β2m in three Chinese chicken lines

Twenty-four BF2 genes and 10 β2m genes from Chinese Sanhuang (SH), Wuji (WJ), and Zhenzhu (ZZ) chicken lines were cloned, and the amino acid replacement rates of the BF2 polypeptide binding domain were investigated. For this purpose, 13 BF2 genes from the SH-chicken line (BF2*01sh-BF2*13sh), six BF2 genes from the WJ-chicken line (BF2*01wj-BF2*06wj), and five BF2 genes from the ZZ-chicken line (BF2*01zz-BF2*05zz) were analyzed. The overall conservation of BF2 alleles could be observed within the sequences, and relative conservation was also displayed in the peptide-binding domain, CD8+ interaction sites, and β2m contact sites. Based on the amino acid similarity, BF2 from the three chicken lines could be divided into eleven gene groups, and five novel gene groups were observed. Although the amino acid similarity among the different alleles was 75.7-99.2%, within an allelic group the members shared >91% amino acid identity with each other. In addition, β2m genes from the three Chinese chicken lines were also clustered into two gene groups: I and II. Between groups I and II, the amino acid identical ratio was much lower (81.9-84.0%). Group I is close to that of the reported chicken β2m, whereas group II represents a new allelic group. The results suggest that five new BF2 groups and a new β2m group exist in the three Chinese chicken lines.