Muscle and Myosin - Strong research slides into place

by David Bradley

Researchers flexed their intellectual muscles at a Royal Society meeting in May to discuss the latest developments of our understanding of the diverse functions of myosin and its role in muscle and motility.

The protein myosin forms the bulk of our muscles. Muscle fibres themselves are made up of bundles of smaller myofibrils, which in turn are composed of units known as sarcomeres. Myosin forms thick filaments interspersed with thin filaments made of a second protein, actin. When a muscle contracts the two sets of filaments slide past each other - a discovery made just fifty years ago and celebrated at the RS meeting.

Since the discovery of the sliding filaments the big question has been: what makes them slide? It turns out that the myosin filaments have appendages known as crossbridges that can cyclically interact with the actin filaments moving them along by a kind of rowing action. The fuel for this process is provided by the breakdown (hydrolysis) of the chemical adenosine triphosphate (ATP), which is the body's energy molecule obtained from the breakdown of sugar.

The myosin crossbridge is the enzyme that hydrolyses ATP to adenosine diphosphate (ADP) and efficiently converts chemical energy into mechanical work. Scientists are now close to understanding the myosin crossbridge in atomic terms as a molecular machine, a wonderful natural example of nanotechnology.

The story of myosin does not, however, stop there. Myosins are also involved in many processes in the cell involving motility, such as the absorption of nutrients, the transport and release of signalling chemicals by nerve cells and even play a crucial role in hearing. Whether you are flexing your biceps or listening to Puccini, myosins are involved.


Part 2 - Mechanism of muscle contraction
Check this article to find out about creatine and muscle growth