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.
Lu H, Fagnant PM, Krementsova EB, Trybus KM (2016) Severe Molecular Defects Exhibited by the R179H Mutation in Human Vascular Smooth Muscle α-Actin. J Biol Chem : .
Sckolnick M, Krementsova EB, Warshaw DM, Trybus KM (2016) Tropomyosin isoforms bias actin track selection by vertebrate myosin Va. Mol Biol Cell 27(19): 2889-97.
Sladewski TE, Krementsova EB, Trybus KM (2016) Myosin Vc Is Specialized for Transport on a Secretory Superhighway. Curr Biol 26(16): 2202-7.
Tang Q, Billington N, Krementsova EB, Bookwalter CS, Lord M, Trybus KM (2016) A single-headed fission yeast myosin V transports actin in a tropomyosin-dependent manner. J Cell Biol 214(2): 167-79.
Lu H, Fagnant PM, Bookwalter CS, Joel P, Trybus KM (2015) Vascular disease-causing mutation R258C in ACTA2 disrupts actin dynamics and interaction with myosin. Proc Natl Acad Sci U S A 112(31): E4168-77.
Sladewski TE, Trybus KM (2014) A single molecule approach to mRNA transport by a class V myosin. RNA Biol 11(8): 986-91.
Bookwalter CS, Kelsen A, Leung JM, Ward GE, Trybus KM (2014) A Toxoplasma gondii class XIV myosin, expressed in Sf9 cells with a parasite co-chaperone, requires two light chains for fast motility. J Biol Chem 289(44): 30832-41.