Myosin VI is perhaps the most unconventional of unconventional myosins. It uses a number of unique mechanisms that are not well understood to accomplish processive movements of similar step sizes to myosin V, but of opposite directionality, for the purposes of anchoring and transporting within cells. Myosin VI can exist as a monomer or a dimer, the cellular significance of which is poorly understood. This project will utilize in vitro expression and functional assays, structural determinations and in vivo assays to attempt to further our understanding of how myosin VI functions and what these molecules do in a cell. These goals will be realized by addressing the following specific aims:
Aim 1. What are the adaptations in the myosin VI converter that create a large and variable (but inherently plus-end directed) step size? Hypothesis: While the unique insert at the end of the myosin VI converter, insert 2, is solely responsible for the reversal of directionality of myosin VI, the myosin VI converter has additional adaptations that allow a unique pre-powerstroke state and create a large and variable step size.
Aim 2. What is the nature and purpose of the unusual myosin VI lever arm + extension? Hypothesis: The large step size of myosin VI is in part due to the unusual movements and conformations of its converter, which creates a larger swing (powerstroke) than for myosin V. With this larger swing, a shorter lever arm can provide the same step size as the myosin V lever arm.
Aim 3. Further probe the mechanism of head gating during processivity Hypothesis: The unique insert, insert 1, of myosin VI is responsible for slow ATP binding, which becomes still slower with reverse strain, while ADP has access to the nucleotide binding pocket. This allows gating of the lead head of a dimer, as well as anchoring of a dimer.
Aim 4. How does myosin VI dimerize and does it function as a dimer or monomer in cells? (collaboration with Karen Avraham) Hypothesis: Myosin VI dimerization is regulated by cargo interactions. We propose that the regulated dimerization obviates the need to regulate motor activity. ? ? ?
| Blanc, Florian; Isabet, Tatiana; Benisty, Hannah et al. (2018) An intermediate along the recovery stroke of myosin VI revealed by X-ray crystallography and molecular dynamics. Proc Natl Acad Sci U S A 115:6213-6218 |
| Wulf, Sarah F; Ropars, Virginie; Fujita-Becker, Setsuko et al. (2016) Force-producing ADP state of myosin bound to actin. Proc Natl Acad Sci U S A 113:E1844-52 |
| Ropars, Virginie; Yang, Zhaohui; Isabet, Tatiana et al. (2016) The myosin X motor is optimized for movement on actin bundles. Nat Commun 7:12456 |
| Houdusse, Anne; Sweeney, H Lee (2016) How Myosin Generates Force on Actin Filaments. Trends Biochem Sci 41:989-997 |
| Llinas, Paola; Isabet, Tatiana; Song, Lin et al. (2015) How actin initiates the motor activity of Myosin. Dev Cell 33:401-12 |
| Pylypenko, Olena; Song, Lin; Shima, Ai et al. (2015) Myosin VI deafness mutation prevents the initiation of processive runs on actin. Proc Natl Acad Sci U S A 112:E1201-9 |
| Mukherjea, Monalisa; Ali, M Yusuf; Kikuti, Carlos et al. (2014) Myosin VI must dimerize and deploy its unusual lever arm in order to perform its cellular roles. Cell Rep 8:1522-32 |
| Nelson, Michael D; Rader, Florian; Tang, Xiu et al. (2014) PDE5 inhibition alleviates functional muscle ischemia in boys with Duchenne muscular dystrophy. Neurology 82:2085-91 |
| Ali, M Yusuf; Previs, Samantha B; Trybus, Kathleen M et al. (2013) Myosin VI has a one track mind versus myosin Va when moving on actin bundles or at an intersection. Traffic 14:70-81 |
| Menetrey, Julie; Isabet, Tatiana; Ropars, Virginie et al. (2012) Processive steps in the reverse direction require uncoupling of the lead head lever arm of myosin VI. Mol Cell 48:75-86 |
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