Of related interest:
Pistol Shrimp, Mantis Shrimp, Archer Fish, Flamboyant Cuttlefish, Invisible Octopus - video
http://www.metacafe.com/watch/4213184/bornagain77
August 13, 2011
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OT: Scientists Discover How Molecular Motors Go Into 'Energy Save Mode' - August 2011
Excerpt: The transport system inside living cells is a well-oiled machine with tiny protein motors hauling chromosomes, neurotransmitters and other vital cargo around the cell. These molecular motors are responsible for a variety of critical transport jobs, but they are not always on the go. They can put themselves into "energy save mode" to conserve cellular fuel and, as a consequence, control what gets moved around the cell, and when.
A new study by Carnegie Mellon University biochemists, published in the Aug. 12 issue of Science, describes how the motors fold in on themselves, or save energy, when their transport services aren't required. ,,, Hackney focuses his research on kinesin-1, the principle motor protein that moves cargo from the nerve cell body down the axon. A typical kinesin molecule has two tails on one end that attach to the cargo and two globular heads on the other end that crank along fibers inside the cell called microtubules, pulling the cargo forward. The movement of the heads, or motor domains, is fueled by the breakdown of ATP, a molecule that stores the energy that drives cellular work. When cargo isn't attached, kinesin folds in upon itself to prevent ATP from being squandered. Although scientists knew that one tail binds to the two heads to keep it in a folded "autoinhibited" state, the molecular mechanism remains unclear. Several possibilities have been proposed, but these latest findings suggest only one solution.
http://www.sciencedaily.com/releases/2011/08/110811151318.htmbornagain77