Troponin C (TnC) is part of the troponin protein complex. There are two subtypes in humans:

• Troponin C, slow skeletal and cardiac muscles (TNNC1) (3p21.1 Online Mendelian Inheritance in Man (OMIM): 191040)
• Troponin C, skeletal muscle (TNNC2) (20q12-q13.11, Online Mendelian Inheritance in Man (OMIM): 191039)

It contains four calcium-binding EF hands, although different isoforms may have fewer than four functional calcium-binding subdomains. It is a component of thin filaments, along with actin and tropomyosin. It contains an N lobe and a C lobe. The C lobe serves a structural purpose and binds to the N domain of troponin I (TnI). The C lobe can bind either Ca²⁺ or Mg²⁺. The N lobe, which binds only Ca²⁺, is the regulatory lobe and binds to the C domain of troponin I after calcium binding.

TnC is structurally similar to calmodulin and myosin light chain. These three groups of proteins form a family.^[1]

• Troponin T
• Troponin I
• Calcium-binding protein
• Sliding filament model

• Troponin+C at the U.S. National Library of Medicine Medical Subject Headings (MeSH)