Phosphorylation of α-tropomyosin (Tpm1.1), a predominant Tpm isoform in the myocardium, is one of the regulatory mechanisms of the heart contractility. The Tpm 1.1 molecule has one site of phosphorylation, Ser283. The degree of the Tpm phosphorylation decreases with age and also changes in heart pathologies. Myocardial pathologies, in particular ischemia, are usually accompanied by pH lowering in the cardiomyocyte cytosol. We studied the effects of acidosis on the structural and functional properties of the pseudo-phosphorylated form of Tpm1.1 with the S283D substitution. We found that in acidosis, the interaction of the N- and C-ends of the S283D Tpm molecules decreases, whereas that of WT Tpm does not change. The pH lowering increased thermostability of the complex of F-actin with S283D Tpm to a greater extent than with WT Tpm. Using an in vitro motility assay with NEM- modified myosin as a load, we assessed the effect of the Tpm pseudo-phosphorylation on the force of the actin-myosin interaction. In acidosis, the force generated by myosin in the interaction with thin filaments containing S283D Tpm was higher than with those containing WT Tpm. Also, the pseudo-phosphorylation increased the myosin ability to resist a load. We conclude that ischemia changes the effect of the phosphorylated Tpm on the contractile function of the myocardium.

α-原肌球蛋白 (Tpm1.1) 是心肌中一种主要的 Tpm 异构体，其磷酸化是心脏收缩力的调节机制之一。Tpm 1.1 分子具有一个磷酸化位点，即 Ser283。Tpm 磷酸化的程度随着年龄的增长而降低，心脏病变也会发生变化。心肌病变，特别是局部缺血，通常伴随着心肌细胞胞质溶胶的 pH 值降低。我们研究了酸中毒对 S283D 取代的 Tpm1.1 假磷酸化形式的结构和功能特性的影响。我们发现在酸中毒中，S283D Tpm 分子的 N 端和 C 端的相互作用减少，而 WT Tpm 的相互作用没有改变。与 WT Tpm 相比，降低 pH 值在更大程度上增加了 F-肌动蛋白与 S283D Tpm 的复合物的热稳定性。使用以 NEM 修饰的肌球蛋白作为负载的体外运动试验，我们评估了 Tpm 假磷酸化对肌动蛋白-肌球蛋白相互作用力的影响。在酸中毒中，肌球蛋白在与含有 S283D Tpm 的细丝相互作用中产生的力高于含有 WT Tpm 的那些。此外，假磷酸化增加了肌球蛋白抵抗负荷的能力。我们得出结论，缺血改变了磷酸化 Tpm 对心肌收缩功能的影响。假磷酸化增加了肌球蛋白抵抗负荷的能力。我们得出结论，缺血改变了磷酸化 Tpm 对心肌收缩功能的影响。假磷酸化增加了肌球蛋白抵抗负荷的能力。我们得出结论，缺血改变了磷酸化 Tpm 对心肌收缩功能的影响。