Abstract

Troponin (Tn) is an essential protein in calcium ion settings of skeletal and heart muscle contractions. It has three subcategories (TnC, TnI, TnT) which are connected to filament actin by tropomyosin. TnC controls the calcium in muscle contraction and is the Ca²⁺-binding subunit of the troponin complex. ATP facilitates separation of myosin from actin filament, eventually making thick filament to slip off thin filament. This results in short sarcomere. In this study, it is investigated that thermodynamics properties increase concentrations of Ca²⁺ and temperature present in lactic acid. Quantum mechanical and molecular dynamics methods were used to analyze the structure and stability of TnC-Ca²⁺configuration. TnC-Ca²⁺ mutated active site in lactic acid and water solvent. Calcium ions approaching TnC caused twisting movement of TnC, so TnI-TnT eventually released the head of Myozin to actin. Increased lactic acid can increase calcium ion connection around TnC and decrease Ca to SR; increased temperature can increase metabolism and fatigue of skeletal muscles, emptying glycolysis and reducing muscle activity.

Key words: Troponin C (TnC), calcium ion (Ca²⁺), lactic acid, fatigue of skeletal muscles, QM/MM.