Quantitative phosphoproteomics analysis of actomyosin dissociation affected by specific site phosphorylation of myofibrillar protein

Abstract Phosphorylation of myofibrillar proteins can regulate muscle contraction and thus affect actomyosin dissociation. To explore the mechanism by which myofibrillar protein phosphorylation and phosphorylation site affects actomyosin dissociation, mass spectrometry-based quantitative phosphoproteomics was used to analyze ovine longissimus thoracis muscles with different actomyosin dissociation. A total of 2073 phosphorylated peptides from 826 phosphoproteins were identified among the myofibrillar proteins of muscles with different actomyosin dissociation, and 176 phosphorylated peptides from 114 phosphoproteins were significantly different (P  high and low group of actomyosin dissociation . Phosphorylation of myosin heavy chain 1 at Ser1896, myosin heavy chain 7 at Thr1019 and Tyr1307 , and titin at Ser265, Ser6085, Ser21930, and Ser26576 can inhibit actomyosin dissociation, whereas phosphorylation of tropomyosin 2 at Ser86, Thr252, and Ser279 contribute to actomyosin dissociation. The phosphorylation sites associated with actomyosin dissociation were mostly serine residues, and the phosphorylation status of myosin regulatory light chain at Ser15 was negatively correlated with actomyosin dissociation. In conclusion, the phosphorylation of some myofibrillar proteins and myosin at specific serine residues may be crucial for actomyosin dissociation.