New paper from our group in Journal of Molecular Biology on the effects of mutations in beta-cardiac myosin heavy chain that cause skeletal muscle diseases: includes our novel approach to investigating mutations on filament formation, using GST-light meromyosin (GST-LMM), which prevents paracrystal formation, allowing filaments to form. Mutations interfere with correct filament formation.
Myosin is a motor protein and is the source of active force in muscle through
its interactions with actin. We are studying it mainly by electron microscopy.
This is being done with the pure protein using conventionally stained specimens
and with frozen-hydrated specimens by cryo-electron microscopy. Image processing
methods are being used to gain more information from the raw micrographs.
Merging of many (currently, up to tens of thousands) images improves resolution
and leads to 3-d models. We are striving for the highest possible resolution
to define structural changes within the molecule. The movie above was obtained
from images of the head regions of muscle myosin (myosin II) and shows evidence
of considerable flexibility within the head. Similar movements may be the
origin of muscle force. We are also working on other non-muscle myosins, for
instance myosin V from brain (see home page).
Recently, we have developed a way to use fast freezing (~10exp7 degC/sec) to trap transient kinetic states in the myosin ATPase cycle and we are studying the conformations of these (collaboration with Dr Howard White, Eastern Virginia Medical School, USA). Such changes in conformation are thought to be the basis of force production. We are also interested in the structural changes that turn force production by myosin on and off.
Most of our myosin work has been done with the skeletal muscle molecule (myosin II). But we have now started work on myosin V which is found in many other tissues, especially brain, and is involved in vesicle transport. The heads of myosin V are about twice as long as the muscle molecule and are thought to walk along actin tracks "processively". This work is a collaboration with Dr Jim Sellers (National Institutes of Health, Washington, USA).
We also collaborate with Dr. G. Offer (Bristol) to model myosin structure at the atomic level, and how myosin molecules pack to form thick filaments.
Professor John Trinick
See also Titin Page.