Structure of the Single-lobe Myosin Light Chain C in Complex with the Light Chain-binding Domains of Myosin-1C Provides Insights into Divergent IQ Motif Recognition

J Biol Chem. 2016 Sep 9;291(37):19607-17. doi: 10.1074/jbc.M116.746313. Epub 2016 Jul 27.


Myosin light chains are key regulators of class 1 myosins and typically comprise two domains, with calmodulin being the archetypal example. They bind IQ motifs within the myosin neck region and amplify conformational changes in the motor domain. A single lobe light chain, myosin light chain C (MlcC), was recently identified and shown to specifically bind to two sequentially divergent IQ motifs of the Dictyostelium myosin-1C. To provide a molecular basis of this interaction, the structures of apo-MlcC and a 2:1 MlcC·myosin-1C neck complex were determined. The two non-functional EF-hand motifs of MlcC pack together to form a globular four-helix bundle that opens up to expose a central hydrophobic groove, which interacts with the N-terminal portion of the divergent IQ1 and IQ2 motifs. The N- and C-terminal regions of MlcC make critical contacts that contribute to its specific interactions with the myosin-1C divergent IQ motifs, which are contacts that deviate from the traditional mode of calmodulin-IQ recognition.

Keywords: EF-hand; IQ motif; light chain; myosin; nuclear magnetic resonance (NMR); protein motif; protein structure; protein-protein interaction; structural biology; x-ray crystallography.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Dictyostelium / enzymology*
  • Dictyostelium / genetics
  • Myosin Light Chains / chemistry*
  • Myosin Light Chains / genetics
  • Myosin Light Chains / metabolism
  • Protein Domains
  • Protozoan Proteins / chemistry*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism


  • Myosin Light Chains
  • Protozoan Proteins

Associated data

  • PDB/1DMO
  • PDB/1QX5
  • PDB/2IX7
  • PDB/2M8U
  • PDB/3CLN
  • PDB/5IBW