betaMHC

Beta-myosin heavy chain (β-MHC) is a cardiac muscle myosin heavy chain isoform that forms part of the motor domain of the myosin II molecule in cardiac muscle. It interacts with actin filaments and uses ATP hydrolysis to generate the contractile force of the heart. The β-MHC isoform is encoded by the MYH7 gene in humans.

In adult human heart, β-MHC is the predominant ventricular myosin heavy chain isoform; α-MHC (MYH6) is expressed at lower levels in the ventricles and is more abundant in atrial tissue and fetal heart. During development and in disease, the relative expression of these isoforms can change.

Biophysically, β-MHC has lower actin-activated ATPase activity and slower cross-bridge cycling than the α isoform, yielding slower contraction velocity but, in many contexts, greater energetic efficiency at sustained workloads.

Clinical relevance: Mutations in MYH7 that encodes β-MHC are among the most common causes of inherited cardiomyopathies, including hypertrophic cardiomyopathy and dilated cardiomyopathy. Alterations in β-MHC expression are observed in heart disease and are used as a molecular marker of ventricular phenotype in some studies.