A team from Rensselaer Polytechnic Institute and the University of Vermont have studied how tiny insects are able to whirl their wings at a dizzying rate of up to 1,000 times per second in order to fly. "We have determined important details of the biochemical reaction by which the fastest known muscle type, insect flight muscle, powers flight," said Douglas Swank, assistant professor of biology at Rensselaer.

Understanding how chemical energy is converted into movements might ultimately be useful in the development of gene therapies against mutations in proteins that detrimentally alter the speed at which, for example, heart muscle fibers contract, provoking heart diseases. "Since insects have been remarkably successful in adapting to a great range of physical and biological environments, in large part due to their ability to fly, the research also will interest scientists studying the evolution of flight," Swank noted.

The team made the research on the fruit fly, focusing on the muscle's main protein, myosin that powers muscle cell contraction. Muscles are divided, accounting their speed, in fast and slow.

In this study, scientists discovered that the chemical reaction mechanism in insect flight muscle is different from that of slow muscle type. "Most research has focused on slower muscle fibers in larger animals," Swank said.

"By investigating extreme examples, e.g. the fastest known muscle type, the mechanisms that differentiate fast and slow muscle fiber types are more readily apparent."

In slow muscles, myosin breaks down adenosine triphosphate (ATP), the muscle, to get energy. Chemically, ATP is divided into two compounds, adenine diphosphate (ADP) and phosphate, each one released from myosin at different rates. In slow muscles, ADP release is the slowest step of the reaction, but in the fast muscle fibers, the team found phosphate release to be the slowest step of the reaction.

The chemical reaction's speed is determined by the slowest step of the reaction. "What we have found is that in the fastest muscle type, ADP release has been sped up to the point where phosphate release is the primary rate-limiting step that determines how fast a muscle can contract," Swank said.

Researchers want to verify the fast muscle contraction's mechanism also in vertebrates, such as the rattlesnake shaker muscle and fast mammalian muscle fibers.