Troponin C is a part of the troponin complex. 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.
The tissue specific subtypes are:
- Slow troponin C, TNNC1 (3p21.3-p14.3, Online 'Mendelian Inheritance in Man' (OMIM) 191040)
- Fast troponin C, TNNC2 (20q12-q13.11, Online 'Mendelian Inheritance in Man' (OMIM) 191039)