Muscle Motor Observed in Action
Myosin proteins have been heavily studied in recent years since they are critical to many cellular and tissue functions, including muscle. According to EurekAlert Scientists from the Burnham Institute for Medical Research and the University of Vermont have captured the first 3-dimensional (3D) atomic-resolution images of the motor protein myosin V as it “walks” along trackways made of actin:
Myosins are a large family of motor proteins that interact with actin filaments for motor movement and muscle contraction. Myosin V is the workhorse of the myosin protein family. It exists to ferry a cargo of proteins needed in a specific place at a specific time. Fueled by hydrolysis — the process of converting the molecule adenosine triphosphate (ATP) into energy — myosin V travels in one direction using actin as a track to deliver its payload of cell vesicles and organelles. Myosin V is also involved in transporting proteins that signal and communicate with other cells.
Myosin V has a two-chained “tail” that diverges to form two “heads” that bind to specific grooves on actin and walk hand over hand along the track, similar to the way a child moves along the monkey bars in a playground. Myosin V differs from the other myosin family proteins in that it is able to sustain this processive motion, enduring many hydrolysis cycles. The other myosins grab on tightly to actin and release after one hydrolysis cycle. (Emphasis added in all citations.)
Using 3D electron cryo-microscopy, the Burnham team took snapshots of the action to put together a sequence that allowed them to visualize myosin in its natural state. They were able to see structural changes in the myosin and the actin, including movement of the “lever arm,” the scientists said.
The tight specs of this molecular machinery were underscored in the press release. “The precise characterization of this myosin-actin interface is critical,” it stated, “evident by the way a single amino acid change in myosin leads to familial hypertrophic cardiomyopathy (FHC), an undetectable condition resulting in death by sudden cardiac arrest in otherwise healthy young adults.”
Pictures say a thousand words, and in this press release the pictures and the words are all about design and nothing about evolution. A key point here is that myosin V is useless without the actin trackway. Considering the horrible impact from even one mutation, this appears to represent an irreducibly complex system – similar to the classic illustration by Michael Behe of a mousetrap, where if a single part is removed, it can no longer function. Suppose a cell was producing thousands of specialized proteins and they had no place to go, or no way to get there. In cells, everything must work together: the cargo, the delivery system, and the recipients.
Evolutionists must explain the emergence of this complex system from simpler precursors, presumably by “co-option” of parts used for other functions. Yet even a “simple” yeast cell contains three classes of myosin needed for key functions (See U of York), so the myosin-actin machinery must have arisen early, even in their own scheme. Some evolutionists believe a mutation in one of the human myosin genes caused our ancestors to have smaller jaws, which then led to the development of bigger brains (see U of Washington article). How can such leaps of imagination be justified when they have yet to explain how myosin evolved in the first place?
The Darwinists are fond of saying that nothing in biology makes sense except in the light of evolution. This is another example of the converse: nothing in Darwinism makes sense in the light of biology – especially when seen with the aid of 3D electron cryo-microscopy. It’s high time to eject the Darwin game CD and get back to the real world.
As you move about today, thank God for Myosin V. His miniature invention provides the power-stroke for our muscles, from every blink of the eye and heartbeat to the most strenuous activity. Recall images of a weight lifter straining every muscle to hoist 472 kg overhead, or a sprinter breaking a 4-minute mile. Those feats are made possible by the collective action of untold myriads of myosin motors burning ATP – itself manufactured by other motors (02/23/2005). Much as we applaud the champion athlete, who really deserves the gold medal?