Biological complexity: glycan layers add to c ell complex it (Introduction)

by David Turell , Sunday, May 10, 2020, 20:30 (1658 days ago) @ David Turell

Glycans, sugar complexes attached to proteins on cell membranes add defenses as well as control of protein traffic in and out:

https://www.quantamagazine.org/sugars-on-coronavirus-spike-protein-offer-vaccine-clues-...

"the surface of a cell is adorned with a forest canopy of sugars, intricate and diverse clusters of carbohydrates that extend like branches and leaves from protein tree trunks. And because that canopy is the face that a cell shows to the world, these complex carbohydrates, or glycans, play a critical role in its encounters and interactions with other cells or molecules.

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"The sheer complexity of sugars makes them more difficult to study. DNA, RNA and proteins are linear molecules built according to defined sets of rules, and scientists have the tools to sequence, analyze and manipulate them. But glycans are branching structures that assemble without a known template. The same site on two identical proteins might be occupied by very different glycans, for instance. Glycans also have exponentially more potential configurations than DNA or proteins: Three different nucleotides can make six distinct DNA sequences; three amino acids can make six unique peptides; three glycan building blocks can form more than a thousand structures. Glycans are flexible, wobbly and variable; intricate, dynamic and somewhat unpredictable.

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“'The sugars aren’t just Christmas lights there to make things happy,” said Victor Nizet, a researcher in pediatric medicine at the University of California, San Diego who specializes in host-microbe interactions and infectious disease. “They’re a critical element of the structure of the house.”

"Glycans help to stabilize proteins and to ensure that they get folded properly. As receptors on the surfaces of cells, they regulate cell function and movement. They’re involved in processes ranging from growth factor signaling to the binding of sperm and egg. They determine a person’s blood type.

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“'They really play an enormous diversity of roles in the body, and we’re kind of just starting to understand the composition of these glycans and where they reside,” said Andrew Ward, a computational biologist at the Scripps Research Institute in California.

"Without taking sugars into account, we can’t fully understand how proteins and cells interact and function. “Imagine a world in which each of us knew only a fraction of the alphabet,” wrote Jamey Marth,"

Comment: The remainder of the article describes how viruses and bacteria use glycans to fool cell defenses. Another intensely complex set of molecules that demand the recognition of the need for design and a designer.