Abstract: Malate dehydrogenase has redox activity and plays a key role in energy metabolism of animal organisms. This study aims to clone the yak MDHI gene,combined with bioinformatics analysis and tissue expression analysis,which may lay a foundation for studying the physical and chemical properties and functions of the yak MDHI gene. The results showed that the cDNA sequence of this gene was 1 169 bp,the CDS region was 1 005 bp in length and it encoded 334 amino acids. The encoded protein was a hydrophilic and stable,which belonged to the conserved domain family. There were two transmembrane areas（located in 6-22 and 34-54 amino acids respectively）and 26 phosphorylation sites（11 Ser phosphorylation sites,11 Thr phosphorylation sites and 4 Tyr phosphorylation sites）. The secondary structure was mainly composed of α-helix（152,accounting for 45.51%）,random coil（110,accounting for 32.93%）. The tertiary structure had a similarity of 98.50% with crystal structure of the ternary complex of cytoplasmic malate dehydrogenase,α-Ketomalonic acid and tetrahydro NAD in porcine. Subcellular localization analysis revealed that most of them were distributed in the endoplasmic reticulum,least in the Golgi and nucleus. Furthermore,homology and phylogenetic tree analysis indicated that its homology was the highest with common cattle,which can be speculate that the yak MDHI gene maybe highly conserved at the evolution level. Tissue expression analysis showed that the gene was expressed the highest in gluteal fat but lower in gluteal muscle,indicating that the gene may function in fat deposition. In sum,we cloned MDHI gene successfully and performed bioinformatics and tissue expression analysis.

Key words: yak, MDHI gene, cloning, bioinformatics analysis, tissue expression