Biological complexity: cell protein transport more defined (Introduction)

by David Turell @, Sunday, February 11, 2018, 20:27 (7 days ago) @ David Turell

Cells transport proteins along actin microtubules tubules with walking molecules that are much more complex than thought and can carry more cargo:

https://phys.org/news/2018-02-microscopic-chariots-molecules-cells.html

"On the cellular highway, motor proteins called dyneins rule the road. Dyneins "walk" along structures called microtubules to deliver cellular cargo, such as signaling molecules and organelles, to different parts of a cell. Without dynein on the job, cells cannot divide and people can develop neurological diseases.

"Now a new study, which appears in the journal Nature Structural & Molecular Biology, provides the first three-dimensional (3D) visualization of the dynein-dynactin complex bound to microtubules. The study leaders from The Scripps Research Institute (TSRI) report that a protein called dynactin hitches two dyneins together, like a yoke locking together a pair of draft horses.

***

"With their new, detailed structure, the researchers noticed a surprising feature: the complex has two dynein molecules where they expected to only see one. This means because each dynein has two motor domains, the dynein-dynactin complex has four motor domains total.

"'This discovery was totally unexpected, and will change how this motor complex is represented in cell biology and biochemistry text books," says Saikat Chowdhury, PhD, a TSRI research associate and co-first author of the study.

"'There had been years of biophysical experiments and biochemical experiments, and it was always assumed that there was just one dynein molecule," Lander adds.

"The researchers could also see where dynactin fit in. They found that the molecule provides a stable scaffold, hitching together the team of motor domains and activating their ability to move along microtubules. This discovery helps explain how dynein can haul large loads, such as organelles that are much bigger than themselves, over long distances in a crowded cellular environment.

"The image processing approach used in this study has the potential to be extremely useful for solving the structures of other large, flexible proteins.

"'We're now able to move past cartoon models and visualize the fine details of many dynamic macromolecular complexes," says Grotjahn. "As we learn more about the 3D organization and architecture of these molecular machines, we will be better equipped to understand how they malfunction in disease.'"

Comment: cells have specific duties in multicellular organisms. Current evolutionary theory offers no suggestion as to how this might have developed stepwise. I suggest it was designed all at once. The complexity of living biology demands a designer


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