Polymorphism, Molecular Characteristics of Alpha-Lactalbumin (LALBA) Gene in River and Swamp Buffalo

Alpha-lactalbumin (α-LA) is a unique whey protein associated with lactation traits in ruminants, but so far, buffalo LALBA gene have not been well understood. In this work, the polymorphisms of LALBA gene in river type and swamp type buffalo were identified using direct sequencing of PCR product. As a result, 26 single nucleotide polymorphisms (SNPs) were determined in the LALBA in two types of buffalo, of which three were located in the 5' untranslated region (UTR), eighteen in the coding sequence (CDS), and five in the 3' UTR, and the variation pattern of LALBA gene was different between two types of buffalo. Ten SNPs in the CDS were non-synonymous, among which the amino acid changes caused by the c.95A>G, c.218A>G, c.286T>G and c.308A>G may affect the function of buffalo α-LA. A total of 11 LALBA CDS haplotypes was defined, of which B1 and B3 haplotypes were shared by river and swamp buffalo and the remains were only found in river buffalo. Accordingly, nine variants and two synonymous variants of buffalo α-LA were inferred, named variant A, A1, A2, B, C, D, E, F, G, H and I, respectively. The length of LALBA CDS for two types of buffalo was 429 nucleotides, encoding a precursor protein of 142 amino acids (AAs), and the first 19 AAs constitute a signal peptide. The composition and physicochemical characteristics of two types of buffalo α-LAs were the same, but slightly different from those of cattle α-LA. The α-LA mature peptides of buffalo and Bos genus contain a LYZ_LA functional domain and their tertiary structures are highly consistent, indicating that they are functionally similar. Our results provided initial insights into the variation, characteristics and biological function of buffalo LALBA gene.