Final answer:
The statement is true; Troponin-C or Calmodulin are crucial Ca2+ binding proteins for muscle contraction control, with Troponin-C involved in skeletal muscle contraction and Calmodulin in smooth muscle contraction.
Step-by-step explanation:
The statement that Troponin-C or Calmodulin are the important Ca2+ binding proteins in the control of muscle contraction, depending on the type of muscle being reviewed, is true. In skeletal muscle, the calcium ions regulate contraction by binding to troponin, including troponin C, which causes conformational changes in the troponins and in turn, moves the tropomyosin to expose the myosin binding sites on the actin filaments. This process is crucial for cross-bridge formation and subsequent muscle contraction.
In contrast, smooth muscle cells do not contain troponin. Instead, cross-bridge formation in smooth muscle is regulated by the protein calmodulin. When calcium ions bind to calmodulin, it activates an enzyme that phosphorylates myosin heads, enabling them to bind to actin and cause muscle contraction. The association of troponin and tropomyosin with actin filaments is essential for skeletal muscle contraction, as depicted in muscle physiology studies using antibodies that localize these proteins.