Kathleen M. Trybus, Ph.D.
Dr. Kathy Trybus received her Ph.D. in 1981 from the University of Chicago in Biophysics. She next went to Brandeis University and worked in a Structural Biology lab in the Rosenstiel Basic Medical Sciences Research Center. In 1998, Dr. Trybus joined the Department faculty at University of Vermont.
A major focus of the laboratory is unconventional myosin V, a processive motor that moves cargo along actin for long distances without dissociating. Two class V myosins from budding yeast (called Myo2p and Myo4p) have captured our interest, since both had been characterized to be non-processive, despite being demonstrated cargo transporters.
Using single molecule and biochemical techniques, we recently showed that Myo2p can only move processively when it walks on actin tracks that resemble those found in the cell. In this case, yeast tropomyosin was found to be essential for the motor to move processively — an elegant demonstration of how the track can affect the motor.
Myo4p, a single-headed class V myosin in budding yeast, transports mRNA to the bud tip. We showed that an oligomeric adapter protein that links the motor to the cargo (She2p) recruits two motors to form a processive complex. Addition of mRNA cargo greatly stabilizes the complex, so that only motors with cargo can move processively. We are altering the mRNA cargo to understand why localizing mRNAs have multiple “zipcode” elements.
Vertebrate myosin Va undergoes a folded (inactive) to extended (active) conformational transition. We are investigating if cargo binding is sufficient to activate the motor, using myoVa-melanophilin-Rab27a-melanosome as a model system.
Another major focus is to understand the molecular mechanisms by which point mutations in smooth muscle actin (ACTA2) lead to vascular disease. These studies are made possible by our ability to express homogeneous wild-type and mutant vertebrate actins in the baculovirus/insect cell expression system. Techniques used to assess defects caused by the mutations include: a TIRF based assay that follows polymerization of single actin filaments in real time, measurement of persistence length to assess structural changes in the filament, and motility assays to quantify how fast smooth muscle myosin can move the actin filaments .
Tropomyosin is essential for Myo2p, a class V myosin in budding yeast, to move processively on actin.
Interactions between two molecular motors coupled to a DNA scaffold.
Trybus KM, Gelfand VI (2013) Molecular motors. Mol Biol Cell 24(6): 672.
Barua B, Fagnant PM, Winkelmann DA, Trybus KM, Hitchcock-Degregori SE (2013) A periodic pattern of evolutionarily-conserved basic and acidic residues constitutes the binding interface of actin- tropomyosin. J Biol Chem : .
Blehm BH, Schroer TA, Trybus KM, Chemla YR, Selvin PR (2013) In vivo optical trapping indicates kinesin’s stall force is reduced by dynein during intracellular transport. Proc Natl Acad Sci U S A 110(9): 3381-6.
Ali MY, Previs SB, Trybus KM, Sweeney HL, Warshaw DM (2013) Myosin VI has a one track mind versus myosin Va when moving on actin bundles or at an intersection. Traffic 14(1): 70-81.
Lu H, Efremov AK, Bookwalter CS, Krementsova EB, Driver JW, Trybus KM, Diehl MR (2012) Collective dynamics of elastically coupled myosin V motors. J Biol Chem 287(33): 27753-61.
Hodges AR, Krementsova EB, Bookwalter CS, Fagnant PM, Sladewski TE, Trybus KM (2012) Tropomyosin is essential for processive movement of a class V myosin from budding yeast. Curr Biol 22(15): 1410-6.
Armstrong JM, Krementsova E, Michalek AJ, Heaslip AT, Nelson SR, Trybus KM, Warshaw DM (2012) Full-length myosin Va exhibits altered gating during processive movement on actin. Proc Natl Acad Sci U S A 109(5): E218-24.