PDBsum entry 2m1u

Contractile protein

PDB id: 2m1u

Contents

Protein chain

93 a.a.

References listed in PDB file

Key reference

• Title: Structure of the small dictyostelium discoideum myosin light chain mlcb provides insights into myob iq motif recognition.
• Authors: J.Liburd, S.Chitayat, S.W.Crawley, K.Munro, E.Miller, C.M.Denis, H.L.Spencer, G.P.Côté, S.P.Smith.
• Ref.: J Biol Chem, 2014, 289, 17030-17042. [DOI no: 10.1074/jbc.M113.536532]
• PubMed id: 24790102

Abstract

Dictyostelium discoideum MyoB is a class I myosin involved in the formation and retraction of membrane projections, cortical tension generation, membrane recycling, and phagosome maturation. The MyoB-specific, single-lobe EF-hand light chain MlcB binds the sole IQ motif of MyoB with submicromolar affinity in the absence and presence of Ca(2+). However, the structural features of this novel myosin light chain and its interaction with its cognate IQ motif remain uncharacterized. Here, we describe the NMR-derived solution structure of apoMlcB, which displays a globular four-helix bundle. Helix 1 adopts a unique orientation when compared with the apo states of the EF-hand calcium-binding proteins calmodulin, S100B, and calbindin D9k. NMR-based chemical shift perturbation mapping identified a hydrophobic MyoB IQ binding surface that involves amino acid residues in helices I and IV and the functional N-terminal Ca(2+) binding loop, a site that appears to be maintained when MlcB adopts the holo state. Complementary mutagenesis and binding studies indicated that residues Ile-701, Phe-705, and Trp-708 of the MyoB IQ motif are critical for recognition of MlcB, which together allowed the generation of a structural model of the apoMlcB-MyoB IQ complex. We conclude that the mode of IQ motif recognition by the novel single-lobe MlcB differs considerably from that of stereotypical bilobal light chains such as calmodulin.