Alpha-actinin-3

Alpha-actinin-3 (also known as ACTN3) is a protein that in humans is encoded by the ACTN3 gene. It is a member of the actin binding proteins, which play a key role in muscle contraction and cell motility.

Function

Alpha-actinin-3 is found in fast-twitch muscle fibers, which are responsible for generating force at high speed. It is thought to contribute to the generation of force during muscle contraction, and variations in the ACTN3 gene have been associated with differences in athletic performance.

Genetics

The ACTN3 gene is located on the chromosome 11. It is expressed only in skeletal muscle. A common variant in the ACTN3 gene causes a change in the alpha-actinin-3 protein, resulting in a nonfunctional version of the protein. This variant is known as the R577X polymorphism.

Clinical significance

Studies have shown that individuals with two nonfunctional copies of the ACTN3 gene (homozygous for the 577X allele) have a significantly lower proportion of fast-twitch muscle fibers and are less likely to excel in power and sprint activities. However, these individuals may have an advantage in endurance activities.

See also

• Actin
• Muscle contraction
• Cell motility