Biological complexity: cellular delivery systems (Introduction)

by David Turell @, Wednesday, May 20, 2020, 15:19 (7 days ago) @ David Turell

Must require design:

"A cell is a large place, like a city to the molecules inside; it is inefficient to store needed cargoes far from their work sites. Within the cell, highways of microtubules grow in the directions that cargo carriers like kinesins need them. Some new discoveries show that additional mechanisms supplement those well-known processes to provide just-in-time delivery.


"At the cellular level, a protein called LPL (lipoprotein lipase) is there to help regulate triglycerides. Lipases are enzymes necessary for the proper distribution and utilization of lipids in the human body, but some of these enzymes can be dangerous if not handled carefully.


"Upon translation in the ribosomes, LPLs in adipocytes are sent to the Golgi apparatus for maturation and proper folding. When ready, they are accompanied by another enzyme, SDC1 (syndecan-1), for sequestration into vesicles. There, a third enzyme named HSPG stabilizes them, rendering them inactive, as two strands of LPL wind into a helical shape. When they get the call for action, they emerge from their vesicles like firefighters at a station, unwind from their helical shape, separate, and hang onto HSPGs on the cell surface.


"A new cellular biology study, published last month in the journal Structure by scientists at Vanderbilt, reports a shape-shifting structure in the human body which plays an important role in the timely delivery of fats and proteins.

"Led by Lauren Jackson, assistant professor of biological sciences and biochemistry at Vanderbilt, the work is the first to visualize this structure — a type of protein complex found in human cells known as retromer — and report its unique ability to transfigure itself into a variety of different architectures and structures.


"Our data suggest the metazoan retromer is an adaptable and plastic scaffold that accommodates interactions with different sorting nexins to sort multiple cargoes from endosomes their final destinations... The retromers can take on a variety of forms, joining in complexes.

“'This flexible scaffold structure plays a key role in the sorting and delivery process,” said Jackson. “These structures reveal how one complex alone is able to sort and deliver cellular ‘cargo’ to different destinations.”


"Proteins are molecular work horses in the cell that perform specific tasks, but it is essential that the timing of protein activities is exquisitely controlled. When proteins have fulfilled their tasks, degradation of these proteins will end processes that are unneeded or detrimental. To control timing, a label — called “ubiquitin” — is attached to unwanted proteins, marking the protein for degradation. Although complex molecular machineries were known to attach ubiquitin, how these machines carry out the labeling process was unknown.


"Sperm can be up to 20 times smaller than a normal cell in the body. And while sperm carry only half as much genetic material as a regular cell, it needs to be folded and packaged in a special way in order to fit. One way nature does this is by replacing histones — proteins around which DNA is wound, like beads on a necklace — with a different type of protein called protamines.

"Thankfully, the fertilized egg knows how to get to the precious genes that helped make you.
Researchers at University of California San Diego School of Medicine have discovered that the enzyme SPRK1 leads the first step in untangling a sperm’s genome, kicking out special packing proteins, which opens up the paternal DNA and allows for major reorganization — all in a matter of hours."

Comment: Same old story. Complexity beyond belief which requires design.

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