Structure of the light chain-binding domain of myosin V

Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 10/2005; 102(36):12718-23. DOI: 10.1073/pnas.0503899102
Source: PubMed


Myosin V is a double-headed molecular motor involved in organelle transport. Two distinctive features of this motor, processivity and the ability to take extended linear steps of approximately 36 nm along the actin helical track, depend on its unusually long light chain-binding domain (LCBD). The LCBD of myosin V consists of six tandem IQ motifs, which constitute the binding sites for calmodulin (CaM) and CaM-like light chains. Here, we report the 2-A resolution crystal structure of myosin light chain 1 (Mlc1p) bound to the IQ2-IQ3 fragment of Myo2p, a myosin V from Saccharomyces cerevisiae. This structure, combined with FRET distance measurements between probes in various CaM-IQ complexes, comparative sequence analysis, and the previously determined structures of Mlc1p-IQ2 and Mlc1p-IQ4, allowed building a model of the LCBD of myosin V. The IQs of myosin V are distributed into three pairs. There appear to be specific cooperative interactions between light chains within each IQ pair, but little or no interaction between pairs, providing flexibility at their junctions. The second and third IQ pairs each present a light chain, whether CaM or a CaM-related molecule, bound in a noncanonical extended conformation in which the N-lobe does not interact with the IQ motif. The resulting free N-lobes may engage in protein-protein interactions. The extended conformation is characteristic of the single IQ of myosin VI and is common throughout the myosin superfamily. The model points to a prominent role of the LCBD in the function, regulation, and molecular interactions of myosin V.

Download full-text


Available from: Grzegorz Rebowski, Oct 08, 2015
31 Reads
  • Source
    • "Instead of the conventional glycine, a residue with a large side-chain (M826) is found and the last arginine of the motif is replaced by a lysine (K830). Modelling studies proposed that this motif could recruit CaM by interaction with the C-lobe only, leaving the N-lobe free in solution (Terrak et al., 2005). However, the structure of the FLA shows that the N-lobe of CaM does interact with the HC helix and its position relative to the HC is analogous to that found for classic IQ motif/CaM complexes. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Myosin VI challenges the prevailing theory of how myosin motors move on actin: the lever arm hypothesis. While the reverse directionality and large powerstroke of myosin VI can be attributed to unusual properties of a subdomain of the motor (converter with a unique insert), these adaptations cannot account for the large step size on actin. Either the lever arm hypothesis needs modification, or myosin VI has some unique form of extension of its lever arm. We determined the structure of the region immediately distal to the lever arm of the motor and show that it is a three-helix bundle. Based on C-terminal truncations that display the normal range of step sizes on actin, CD, fluorescence studies, and a partial deletion of the bundle, we demonstrate that this bundle unfolds upon dimerization of two myosin VI monomers. This unconventional mechanism generates an extension of the lever arm of myosin VI.
    Molecular cell 09/2009; 35(3):305-15. DOI:10.1016/j.molcel.2009.07.010 · 14.02 Impact Factor
  • Source
    • "In summary, we have identified two proteins, Ypt32p and Mlc1p, that are able to interact with the VBR of Myo2p opening up the possibility of defining how the interaction of the Myo2p GTD with organelle-linked receptors and Ypt32p-associated carriers is regulated. The high functional and structural conservation among phylogenetically distant myosin V of the patches of residues identified here as important for Ypt32p and Mlc1p binding (Pashkova et al., 2006; Weisman, 2006), the known ability of the Ypt32p-related Rab11 protein to interact with Myosin V GTD (Hales et al., 2002; Fielding et al., 2005) as well as the high conservation of essential light chains in structure and function throughout the evolution (Bahler and Rhoads, 2002; Terrak et al., 2005) strongly suggest that the interactions identified here are reciprocated in mammalian cells. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Myosin V is an actin-based motor essential for a variety of cellular processes including skin pigmentation, cell separation and synaptic transmission. Myosin V transports organelles, vesicles and mRNA by binding, directly or indirectly, to cargo-bound receptors via its C-terminal globular tail domain (GTD). We have used the budding yeast myosin V Myo2p to shed light on the mechanism of how Myo2p interacts with post-Golgi carriers. We show that the Rab/Ypt protein Ypt32p, which associates with membranes of the trans-Golgi network, secretory vesicles and endosomes and is related to the mammalian Rab11, interacts with the Myo2p GTD within a region previously identified as the 'vesicle binding region'. Furthermore, we show that the essential myosin light chain 1 (Mlc1p), required for vesicle delivery at the mother-bud neck during cytokinesis, binds to the Myo2p GTD in a region overlapping that of Ypt32p. Our data are consistent with a role of Ypt32p and Mlc1p in regulating the interaction of post-Golgi carriers with Myo2p subdomain II.
    Molecular Microbiology 04/2008; 67(5):1051-66. DOI:10.1111/j.1365-2958.2008.06106.x · 4.42 Impact Factor
  • Source
    • "It is also possible that CaBP1 competes for IQ binding with a single, loosely-bound lobe of calmodulin. Single-lobe light-chain binding has been proposed for Mlc1p binding to the IQ motifs of myosin-V (Terrak et al. 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Myo1c is a member of the myosin-I family that binds phosphoinositides and links the actin cytoskeleton to cellular membranes. Recent investigations suggest that targeting of myo1c to some subcellular regions requires the binding of an unknown protein to the IQ motifs in the myo1c regulatory domain. We identify two myristoylated proteins that bind the myo1c regulatory domain: calcium-binding protein 1 (CaBP1) and calcium- and integrin-binding-protein-1 (CIB1). CIB1 and CaBP1 interact with myo1c in vivo as determined by pull-down experiments and fluorescence microscopy where the endogenously expressed proteins show extensive cellular colocalization with myo1c. CIB1 and CaBP1 bind to the myo1c IQ motifs in the regulatory domain where they compete with calmodulin for binding. CaBP1 has a higher apparent affinity for myo1c than CIB1, and both proteins better compete with calmodulin in the presence of calcium. We propose that these proteins may play a role in specifying subcellular localization of myo1c.
    Journal of Muscle Research and Cell Motility 02/2007; 28(6):285-91. DOI:10.1007/s10974-007-9124-7 · 2.09 Impact Factor
Show more