MYL9

MYL9 or Myosin Light Chain 9 is a protein that in humans is encoded by the MYL9 gene. It is a regulatory light chain of myosin II, a protein complex responsible for muscle contraction. MYL9 is expressed in smooth muscle tissues, where it plays a crucial role in muscle contraction and relaxation.

Structure

The MYL9 gene is located on the short (p) arm of chromosome 20 at position 13.2, specifically from base pair 44,296,811 to base pair 44,299,834. The MYL9 protein is a small, regulatory light chain with a molecular weight of approximately 20 kDa. It consists of 166 amino acids and has a structure typical of regulatory light chains, with two EF-hand motifs that bind calcium ions.

Function

MYL9 is a component of the myosin II complex, which is a motor protein essential for muscle contraction. It interacts with the heavy chain of myosin II to regulate its ATPase activity, thereby controlling the speed of muscle contraction. In smooth muscle tissues, MYL9 is phosphorylated by myosin light chain kinase (MLCK) in response to increases in intracellular calcium levels. This phosphorylation event triggers the contraction of smooth muscle cells.

Clinical Significance

Alterations in the MYL9 gene or its protein product have been associated with various pathological conditions. For instance, mutations in MYL9 have been linked to hypertrophic cardiomyopathy, a condition characterized by the thickening of the heart muscle. Additionally, changes in the expression levels of MYL9 have been observed in certain types of cancer, suggesting a potential role in tumorigenesis.

See Also

• Myosin
• Myosin light chain kinase
• Hypertrophic cardiomyopathy