Biological complexity: how molecules enter cell walls (Introduction)

by David Turell , Wednesday, October 20, 2021, 19:40 (919 days ago) @ David Turell

Giant ones were doing it in an unknown way until now:

https://phys.org/news/2021-10-magic-proteins-cell-walls.html

"For decades, scientists have wondered how large molecules such as proteins pass through cell walls, also known as plasma membranes, without leaving a trace. That ability is part of what makes certain drugs—including some cancer treatments and the COVID-19 vaccine—work. And it is also how bacterial toxins enter human cells and wreak havoc.

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"'It is almost like a magic trick, the way the membrane encapsulates these toxins," said Dehua Pei, senior author of the study and a professor of chemistry and biochemistry at The Ohio State University.

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"While working on the team's other projects, Sahni noticed that some fragments of proteins, known as peptides, cross membranes by pushing against them. The peptides deformed the membrane into small circular buds. The buds then detach as small bubbles, known as vesicles, which eventually "pop," allowing the peptides to be released inside the cell. The team subsequently observed that two structurally different bacterial toxins also employed this same mechanism. This discovery led them to conclude that this budding-and-collapse mechanism is a common mechanism employed by many large biomolecules.

"'This budding-and-collapse phenomenon was previously unknown, but we were able to witness it because we had the equipment, training and experience to know what we were looking at," Sahni said.

"The team witnessed the budding-and-collapse in live cells through confocal microscopy, an imaging technique that allowed them to focus in on what was happening inside the cells, and on the cell membranes, with these specific proteins."

Comment: All of this must be tightly controlled in the general metabolic homeostasis or there would be chaos in the byplay of cells asking for molecules. At the very necessary high speeds it must be automatically guided.