Troponin C is a protein which is part of the

troponin image:Troponin Ribbon Diagram.png, 400px, Ribbon representation of the human cardiac troponin core complex (52 kDa core) in the calcium-saturated form. Blue = troponin C; green = troponin I; magenta = troponin T.; ; rendered with PyMOL Troponin, ...

complex. It contains four calcium-binding

EF hand The EF hand is a helix–loop–helix structural domain or ''motif'' found in a large family of calcium-binding proteins. The EF-hand motif contains a helix–loop–helix topology, much like the spread thumb and forefinger of the human hand, i ...

s, although different isoforms may have fewer than four functional calcium-binding subdomains. It is a component of

thin filament Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the ''contractile proteins'' and titin is an elastic protein. The myofilaments act together ...

s, along with

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ov ...

and

tropomyosin Tropomyosin is a two-stranded alpha-helical, coiled coil protein found in actin-based cytoskeletons. Tropomyosin and the actin skeleton All organisms contain organelles that provide physical integrity to their cells. These type of organelles a ...

. 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 Troponin I is a cardiac and skeletal muscle protein family. It is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place. Troponin I prevents myosin from binding to ac ...

(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.

Isoforms

The tissue specific subtypes are: * Slow troponin C,

TNNC1 Troponin C, also known as TN-C or TnC, is a protein that resides in the troponin complex on actin thin filaments of striated muscle (cardiac, fast-twitch skeletal, or slow-twitch skeletal) and is responsible for binding calcium to activate muscle ...

(3p21.1 ) * Fast troponin C,

TNNC2 Troponin C, skeletal muscle is a protein that in humans is encoded by the ''TNNC2'' gene. Troponin (Tn), is a key protein complex in the regulation of striated muscle contraction, composed of three subunits. The TnI subunit inhibits actomyosin ...

(20q12-q13.11, )

Mutations

Point mutations can occur in troponin C inducing alterations to Ca²⁺ and Mg²⁺ binding and protein structure, leading to abnormalities in muscle contraction. In cardiac muscle, they are related to

dilated cardiomyopathy Dilated cardiomyopathy (DCM) is a condition in which the heart becomes enlarged and cannot pump blood effectively. Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Co ...

(DCM) and hypertrophic cardiomyopathy (HCM). These known point mutations are: *

A8V A8V is point mutation on Troponin C (cTNC) that leads to a hypertrophic cardiomyopathy. The coordinated cardiac muscle contraction is regulated by the troponin complex on thin filament (troponin C which is calcium binding, troponin T that plays the ...

D145E D145E is a point mutation on troponin C that leads to hypertrophic cardiomyopathy disease. This mutation is caused by the change of nucleotide C to A at nucleotide 435, switching the amino acid aspartic acid to glutamic acid, which is located at ...

* A31S * C84Y * E134D * Y5H * I148V

References

External links

* {{Calcium-binding proteins Troponin

Isoforms

Mutations

See also

References

External links