Biological complexity: protein switches in action (Introduction)

by David Turell , Tuesday, December 24, 2019, 18:46 (1796 days ago) @ David Turell

One protein molecule turning on another to function is an automatic activity that requires no intelligence. In this study automatic cell skeleton formation is triggered by molecular interactions:

https://www.sciencedaily.com/releases/2019/12/191223122857.htm

"The goal was to identify the proteins that attach to those of the Rho family, famous in the cell biology world since the discovery in the early 1990s that they dictate how pieces of the cell skeleton -- the "cytoskeleton" -- are assembled.

"In humans, the 20 members of the Rho family are scattered on the inner surface of cell membranes and act like small switches. When a signal from outside or inside the cell activates them, they stimulate other proteins to force the cytoskeleton to add or remove parts to its framework.

"Out of all these proteins, only three, to date, have been thoroughly studied by researchers: Cdc42, Rac1 and RhoA. Cdc42 acts as the lead protein: it indicates the path that white blood cells must take to find a site of infection. Rac1 activates the engines that drive a non-muscular cell forward. RhoA stimulates the formation of fibres that allow cells to contract or form resistant tissues as they come together to produce, for example, the wall of a blood vessel.

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"Using 28 two-headed proteins and presenting the GTPases -- a superfamily of enzymes that function as 'molecular switches' and are involved in regulating many cellular processes -- in both active and inactive configurations, the team caught a total of 9,939 proteins. Some were already known to the scientists, including the GTPases' activators and deactivators. But the researchers also discovered hundreds of individual proteins with yet-to-be-defined roles.

"These discoveries include the missing link of the cytoskelton Rho process identified in the early '90s. Back then, researchers noticed that the RhoA protein indirectly activates another protein, ERM, causing it to stabilize the cytoskeleton. But they didn't know the precise mechanism behind this process. On their "fishing expedition," Côté and his team found the answer: what forges the link between RhoA and ERM is a protein called SLK.

"In their study, the IRCM team also looked at other proteins that, until now, were virtually unknown to biologists, namely GARRE and PLEKHG3. The scientists demonstrated that these proteins naturally attach to the active forms of Rac1 and RhoG, respectively. "

Comment: The cells' genome contain information/instructions to initiate these automatic protein molecules to react with each other producing cellular skeletons. No thought involved.