ObjectiveTo explore the sequence characteristic of human leptin protein and to establish protein-protein interaction (PPI) network. MethodsThe bioinformatic analysis tools in terms of Expasy online data analyzer, TMHMM-2.0 online website, SOPMA secondary structure prediction method, STRING database, and Molecular Evolutionary Genetics Analysis 7.0 software, etc., were used to analyze physico-chemical property, structure, PPI network, phylogenetic tree on human leptin protein. ResultsHuman leptin protein contained 167 amino acid residues, its molecular formula was C842H1333N217O245S7, its relative molecular mass was around 18 640.57, its theoretical isoelectric point was 5.88, its instability coefficient was 47.52, and its average hydrophilic coefficient was 0.131. Amino terminal of human leptin protein possessed signal peptide, which belonged to secreted protein and contained phosphorylated locus, and was lipoprotein existed mainly in extra cell. Secondary structure of human leptin protein was mainly α-helix (accounting for 57.49%), followed by irregular crimp (accounting for 32.34%), extended chain (accounting for 7.78%), and β rotation (accounting for 2.4%); moreover, its tertiary structure exhibited similar prediction results with the secondary structure, and the similarity to the template sequence reached up to 99.32%. The PPI network revealed that protein family interacting with human leptin protein contained LEPR, GHRL, GCG, IAPP, PPARG, STAT3, SOCS3, JAK2, NPY, and PTPN1. The results of phylogenetic tree indicated that human leptin protein was closely related to Pan troglodytes. ConclusionHuman leptin protein possesses structure of signal peptide, which belongs to non-glycosylated secreted protein, and may interact with LEPR, GHRL, GCG, IAPP, PPARG, STAT3, SOCS3, JAK2, NPY, and PTPN1 proteins; in addition, the change of its protein expression in peripheral blood circulation system may lead to immune dysfunction.

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