1n2d
From Proteopedia
Ternary complex of MLC1P bound to IQ2 and IQ3 of Myo2p, a class V myosin
Structural highlights
Function[MLC1_YEAST] Essential light chain for the class II conventional myosin MYO1. Acts also as light chain for the class V unconventional myosin MYO2 and for IQG1. Involved in the assembly of the contractile actomyosin ring at the bud neck during cytokinesis by recruiting IQG1 to the bud neck. Also required for chitin and MYO2-dependent secretory vesicle deposition to the center of the bud neck for septum formation. May stabilize MYO2 by binding to its IQ domains. Its major function is probably not to regulate MYO1 activity, but rather to coordinate actin ring formation and targeted membrane deposition during cytokinesis via its interactions with MYO1, IQG1 and MYO2.[1] [2] [3] [MYO2_YEAST] Myosin heavy chain that is required for the cell cycle-regulated transport of various organelles and proteins for their segregation. Functions by binding with its tail domain to receptor proteins on organelles and exerting force with its N-terminal motor domain against actin filaments, thereby transporting its cargo along polarized actin cables. Essential for the delivery of secretory vesicles to sites of active growth during bud emergence and cytokinesis. Required for segregation and inheritance of peroxisomes, late Golgi compartments, mitochondria and the vacuole to the daughter cell during cell division. Also required for correct alignment of the spindle during mitosis.[4] [5] [6] [7] [8] [9] [10] [11] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMyosin 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. Structure of the light chain-binding domain of myosin V.,Terrak M, Rebowski G, Lu RC, Grabarek Z, Dominguez R Proc Natl Acad Sci U S A. 2005 Sep 6;102(36):12718-23. Epub 2005 Aug 24. PMID:16120677[12] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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