Abstract: The purpose of this study was to analyze the data of embryonic skeletal muscle proteomic in sheep, and provide a basis for revealing the mechanism of embryonic skeletal muscle development and growth in sheep. In previous proteomic study, the embryonic longissimus dorsi proteins were quantified by using tandem mass tag (TMT) in the adult Chinese merino ewes on the Day 85 (D85), 105 (D105) and 135 (D135) of gestation, and 3 comparable groups D85/D105, D105/D135 and D85/D135 were set up. The KEGG and parallel reaction monitoring (PRM) methods were used to analyze and verify the up-and down-regulation differential abundance proteins in sheep embryonic skeletal muscle in 3 comparable groups, and bioinformatics analysis was performed for the candidate proteins. The marker protein about muscle fibers maturation and differentiation of myosin-2 isoform X2 (MYH) was verified by PRM, the results demonstrated that the change trend of MYH was consistent with the trend of sheep embryonic muscle fiber maturation and differentiation. The up-regulation and down-regulation differential abundance proteins were analyzed by KEGG method, the results showed that the up-regulation differen-tial abundance proteins in D105/D85 comparable group were significantly enriched in insulin signaling pathway, and the down-regulation differential abundance proteins in D135/D105 and D135/D85 comparable groups were significantly enriched in DNA replication and protein digestion and absorption signaling pathways. The muscle development related proteins, cAMP-dependent protein kinase catalytic subunit alpha (PRKACA) and glucose transporter member 4 isoform X1 (GLUT4), were significantly enriched in insulin signaling pathway. The bioinformatics analysis of the two proteins revealed that the theoretical molecular weight of PRKACA and GLUT4 were 121.73 and 20.64 ku, respectively. The PRKACA contained 147 positively charged amino acid residues and 135 negatively charged amino acid residues, the theoretical isoelectric point was 8.81, the hydrophilic average coefficient was -0.408; and the GLUT4 contained 12 positively charged amino acid residues and 12 negatively charged amino acid residues, the theoretical isoelectric point was 6.54, the hydrophilic average coefficient was 0.811. There were no N-terminal glycosylation site and there was 45 phosphorylation sites in PRKACA; there was an N-terminal glycosylation site and 25 phosphorylation sites in GLUT4. The homology of PRKACA and CAMP-2 relies on the chimeric fusion crystal structure of protein kinase a was 85% in tertiary structure, the homology of the GLUT4 and human glucose transporter GLUT1 was 78% in tertiary structure. The results showed that the trend of MYH quantification verified by PRM was consistent with the trend of embryonic muscle fiber maturation and differentiation. PRKACA and GLUT4 were important candidate proteins, with abundant phosphorylation sites, involved in the regulating of insulin signaling pathway.

Key words: sheep, embryonic skeletal muscle, parallel reaction monitoring, proteomics