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Myosin, light chain 3, alkali; ventricular, skeletal, slow
Symbols MYL3 ; CMH8; MLC1SB; MLC1V; VLC1
External IDs OMIM160790 MGI97268 HomoloGene20099 GeneCards: MYL3 Gene
RNA expression pattern
PBB GE MYL3 205589 at tn.png
More reference expression data
Species Human Mouse
Entrez 4634 17897
Ensembl ENSG00000160808 ENSMUSG00000059741
UniProt P08590 P09542
RefSeq (mRNA) NM_000258 NM_010859
RefSeq (protein) NP_000249 NP_034989
Location (UCSC) Chr 3:
46.9 – 46.92 Mb
Chr 9:
110.76 – 110.77 Mb
PubMed search [1] [2]

Myosin essential light chain (ELC), ventricular/cardiac isoform is a protein that in humans is encoded by the MYL3 gene.[1][2][3]This cardiac ventricular/slow skeletal ELC isoform is distinct from that expressed in fast skeletal muscle (MYL1) and cardiac atrial muscle (MYL4).

Structure and function[edit]

Cardiac, ventricular ELC (21.9 kDa) and the second light chain, regulatory light chain (RLC, MYL2), are non-covalently bound to IQXXXRGXXXR motifs in the 9 nm S1-S2 lever arm of the MHC head,[4] both alpha (MYH6) and beta (MYH7) isoforms. Both light chains are members of the EF-hand superfamily of proteins, which possess helix-loop-helix motifs in two globular domains connected by an alpha-helical linker. Though EF hand motifs are specialized to bind divalent ions such as calcium, cardiac ELC does not bind calcium at physiological levels.[5] The N-terminal region of cardiac ELC is functionlly unique in that it is positively charged, being rich in Lysine residues (amino acids 4-14), with subsequent unique structure governed by Proline-Alanine repeats (amino acids 15-36).

Studies have provided evidence for ELC as modulator of myosin crossbrige kinetics. Treating cardiac myofibrils with the Lysine-rich N-terminal peptide (amino acids 5-14) evoked a supramaximal increase in cardiac myofibrillar MgATPase activity at submaximal calcium concentrations,[6] and further studies demonstrated that this region of ELC modulates the affinity of myosin for actin.[7]

Clinical significance[edit]

Mutations in MYL3 have been identified as a cause of mid-left ventricular chamber type hypertrophic cardiomyopathy.[3]


  1. ^ Shi Q, Li R, Mickle D, Jackowski G (Nov 1992). "Analysis of the upstream regulatory region of human ventricular myosin light chain 1 gene". Journal of Molecular and Cellular Cardiology 24 (11): 1221–9. doi:10.1016/0022-2828(92)93089-3. PMID 1479618. 
  2. ^ Cohen-Haguenauer O, Barton P, Van Cong N, Cohen A, Masset M, Buckingham M et al. (Feb 1989). "Chromosomal assignment of two myosin alkali light-chain genes encoding the ventricular/slow skeletal muscle isoform and the atrial/fetal muscle isoform (MYL3, MYL4)". Human Genetics 81 (3): 278–82. doi:10.1007/bf00279004. PMID 2784124. 
  3. ^ a b "Entrez Gene: MYL3 myosin, light chain 3, alkali; ventricular, skeletal, slow". 
  4. ^ Rayment I, Rypniewski W, Schmidt-Bäse K, Smith R, Tomchick D, Benning M et al. (1993). "Three-dimensional structure of myosin subfragment-1: a molecular motor". Science 261 (5117): 50–8. PMID 8316857. 
  5. ^ Collins J (1991). "Myosin light chains and troponin C: structural and evolutionary relationships revealed by amino acid sequence comparisons". J. Muscle Res. Cell. Motil. 12 (1): 3–25. PMID 2050809. 
  6. ^ Rarick H, Opgenorth T, von Geldern T, Wu-Wong J, Solaro R (1996). "An essential myosin light chain peptide induces supramaximal stimulation of cardiac myofibrillar ATPase activity". J. Biol. Chem. 271 (43): 27039–43. PMID 8900193. 
  7. ^ Stepkowski D, Efimova N, Paczyņska A, Moczarska A, Nieznańska H, Kakol I (1997). "The possible role of myosin A1 light chain in the weakening of actin-myosin interaction". Biochim. Biophys. Acta 1340 (1): 105–14. PMID 9217020. 

Further reading[edit]

External links[edit]