37QC

Human beta-cardiac myosin S1 motor domain carrying the E525K mutation with the essential light chain in the pre-powerstroke state

Summary for 37QC

• Entry DOI: 10.2210/pdb37qc/pdb
• EMDB information: 78403
• Descriptor: Myosin-7,Green fluorescent protein, Myosin light chain 1/3, skeletal muscle isoform, PHOSPHATE ION, ... (4 entities in total)
• Functional Keywords: cardiac myosin, motor domain, essential light chain, dilated cardiomyopathy, contractile protein, actin binding, adp, phosphate
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 2
• Total formula weight: 147628.22

Authors

Somavarapu, A.K.,Gautam, R.,Craig, R.,Padron, R. (deposition date: 2026-07-31, release date: 2026-11-04)

Primary citation

Gautam, R.,Somavarapu, A.K.,Robeson, K.Z.,Childers, M.C.,Regnier, M.,Ge, J.,Yengo, C.M.,Craig, R.,Padron, R.
The dilated cardiomyopathy E525K mutation stabilizes the cardiac myosin interacting-heads motif while activating the isolated motor domain.
Biorxiv, 2026

PubMed Abstract: Mutations in β-cardiac myosin are a common cause of inherited cardiomyopathies. The dilated cardiomyopathy E525K mutation alters both thick filament regulation and motor activity, yet the structural basis for these effects has remained unclear. Here, we combined cryo-EM and MD simulations to determine how E525K affects the conformational landscape of cardiac myosin in both its autoinhibited interacting-heads motif (IHM) and isolated myosin head states. E525K-mutated myosin exclusively adopted a single S2 conformation in IHM, in contrast to the conformational heterogeneity observed in wild-type myosin. Structural and electrostatic analyses revealed that the mutation increased positive charge density at the blocked-head (BH) - S2 (subfragment-2) interface, strengthening interactions with negatively charged residues within S2. 3D variability analysis and MD simulations of the E525K IHM demonstrated reduced S2 mobility, consistent with strengthened BH - S2 interactions, and decreased conformational flexibility, providing a structural mechanism for stabilization of the IHM state. To investigate the isolated myosin head, we determined cryo-EM structures of wild-type and E525K subfragment-1 (S1). The mutation induced local conformational rearrangements in the activation-loop and Loop 3 region, the SH3-like domain, and the essential light chain of S1, revealing structural changes that support the enhanced motor activity previously reported for isolated E525K myosin motors. These findings show that E525K stabilizes the autoinhibited IHM through electrostatic stabilization of the BH - S2 interface while inducing structural changes consistent with activation of the isolated motor domain, providing structural insights into how a single DCM mutation differentially regulates cardiac myosin S1 and IHM structure and function.

PubMed: 42926450
DOI: 10.64898/2026.10.02.756299

Experimental method

ELECTRON MICROSCOPY (3.3 Å)