Molecular cloning and sequence analysis of hepatic lipase gene in yak

In order to study the biological function of hepatic lipase (hi) gene in yak, the cDNA sequence encoding hepatic lipase from yak was cloned by RT-PCR method using gene specific PCR primers. The cloned cDNA fragment (1540 bp) contained a 1503 bp open reading frame, encoded 500 amino acids (AAs) with a molecular mass of 56.734 kDa. It showed a high level of sequence identity to Bos Taurus (99.40%), Homo sapiens (77.64%), Oryctolagus cuniculus (76.20%), Mus musculus (68.88%), Xenopus laevis (55.27%) andDanio rerio (47.69%). The hi gene was expressed only in liver tissue and not in heart, spleen, kidney and brain tissues. Further analysis of yak HL amino acid sequence implied that it contained a complete lipase active site (VHLIGYSLGA) ranging from 162 to 171 amino acid residues. It also contained two conserved domains, conserved lipase domain (18AAs-350AAs) in its N-terminal and the PLAT domain (353AAs-488AAs) in its C-terminal. The phylogenetic analysis showed that yak and Bos taurus were the closest species. The prediction of secondary structures indicated that HL of yak had the similar secondary structure with other isolated HL. The results of this study suggested that hi gene of yak was similar with Bos taurus and was expressed only in liver tissue.