MYH7
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3DTP, 4DB1, 4P7H, 4XA1, 4XA3, 4XA4, 4XA6, 4PA0, 5CHX, 5CJ0, 5CJ4, 5CJ1, 2FXO, 2FXM
Identifiers
Aliases	MYH7, CMD1S, CMH1, MPD1, MYHCB, SPMD, SPMM, myosin, heavy chain 7, cardiac muscle, beta, myosin heavy chain 7
External IDs	OMIM: 160760 MGI: 2155600 HomoloGene: 68044 GeneCards: MYH7
Gene location (Human) Chr. Chromosome 14 (human)[1] Band 14q11.2 Start 23,412,740 bp[1] End 23,435,660 bp[1]
Gene location (Mouse) Chr. Chromosome 14 (mouse)[2] Band 14 C3|14 28.01 cM Start 55,208,141 bp[2] End 55,232,083 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in gastrocnemius muscle right ventricle left ventricle triceps brachii muscle vastus lateralis muscle thoracic diaphragm deltoid muscle tibialis anterior muscle body of tongue body of pancreas Top expressed in soleus muscle atrioventricular valve endocardial cushion ankle plantaris muscle extraocular muscle thoracic diaphragm intercostal muscle internal carotid artery gastrocnemius muscle More reference expression data BioGPS More reference expression data
Gene ontology Molecular function nucleotide binding calmodulin binding protein binding actin binding cytoskeletal motor activity ATP binding ATPase activity microfilament motor activity actin filament binding microtubule motor activity microtubule binding Cellular component cytoplasm stress fiber Z disc myosin filament myosin complex muscle myosin complex myofibril sarcomere Biological process cardiac muscle contraction adult heart development transition between fast and slow fiber regulation of the force of heart contraction skeletal muscle contraction regulation of slow-twitch skeletal muscle fiber contraction regulation of heart rate ventricular cardiac muscle tissue morphogenesis ATP metabolic process muscle filament sliding striated muscle contraction regulation of the force of skeletal muscle contraction muscle contraction cardiac muscle hypertrophy in response to stress microtubule-based movement Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 4625 140781 Ensembl ENSG00000092054 ENSMUSG00000053093 UniProt P12883 Q91Z83 RefSeq (mRNA) NM_000257 NM_080728 NM_001361607 RefSeq (protein) NP_000248 NP_542766 NP_001348536 Location (UCSC) Chr 14: 23.41 – 23.44 Mb Chr 14: 55.21 – 55.23 Mb PubMed search [3] [4]
Wikidata
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MYH7 is a gene encoding a myosin heavy chain beta (MHC-β) isoform (slow twitch) expressed primarily in the heart, but also in skeletal muscles (type I fibers).^[5] This isoform is distinct from the fast isoform of cardiac myosin heavy chain, MYH6, referred to as MHC-α. MHC-β is the major protein comprising the thick filament that forms the sarcomeres in cardiac muscle and plays a major role in cardiac muscle contraction.^[6]

Structure

MHC-β is a 223 kDa protein composed of 1935 amino acids.^[7][8] MHC-β is a hexameric, asymmetric motor forming the bulk of the thick filament in cardiac muscle. MHC-β is composed of N-terminal globular heads (20 nm) that project laterally, and alpha helical tails (130 nm) that dimerize and multimerize into a coiled-coil motif to form the light meromyosin (LMM), thick filament rod.^[9] The 9 nm alpha-helical neck region of each MHC-β head non-covalently binds two light chains, essential light chain (MYL3) and regulatory light chain (MYL2).^[10] Approximately 300 myosin molecules constitute one thick filament.^[11] There are two isoforms of cardiac MHC, α and β, which display 93% homology. MHC-α and MHC-β display significantly different enzymatic properties, with α having 150-300% the contractile velocity and 60-70% actin attachment time as that of β.^[12][13] MHC-β is predominately expressed in the human ventricle, while MHC-α is predominantly expressed in human atria.

Function

It is the enzymatic activity of the ATPase in the myosin head that cyclically hydrolyzes ATP, fueling the myosin power stroke. This process converts chemical to mechanical energy, and propels shortening of the sarcomeres in order to generate intraventricular pressure and power. An accepted mechanism for this process is that ADP-bound myosin attaches to actin while thrusting tropomyosin inwards,^[14] then the S1-S2 myosin lever arm rotates ~70° about the converter domain and drives actin filaments towards the M-line.^[15]

Clinical significance

Several mutations in MYH7 have been associated with inherited cardiomyopathies. Lowrance et al. were the first to identify the causative mutation Arg403Gln for hypertrophic cardiomyopathy (HCM) in the MYH7 gene.^[16] Studies have since identified several more MYH7 mutations, that are estimated to be causal in approximately 40% of HCM cases. This condition is an autosomal-dominant disease, in which a single copy of the variant gene causes enlargement of the left ventricle of the heart. Disease onset usually occurs later in life, perhaps triggered by changes in thyroid hormone function and/or physical stress.

Another condition associated to mutations in this gene is paraspinal and proximal muscle atrophy.^[17]

References

Further reading

External links

• Mass spectrometry characterization of MYH7 at COPaKB Archived 4 March 2016 at the Wayback Machine
• GeneReviews/NIH/NCBI/UW entry on Familial Hypertrophic Cardiomyopathy Overview
• GeneReviews/NCBI/NIH/UW entry on Laing Distal Myopathy
• MYH7+protein,+human at the U.S. National Library of Medicine Medical Subject Headings (MeSH)