The biochemistry of cell communication (Introduction)

by David Turell , Wednesday, January 18, 2017, 00:48 (2653 days ago) @ dhw

How mRNA molecules are delivered to the right spot in the cell for protein production is now understood:

https://www.sciencedaily.com/releases/2017/01/170117083037.htm

"Messenger RNAs bearing the genetic information for the synthesis of proteins are delivered to defined sites in the cell cytoplasm by molecular motors.

***

"The research team systematically isolated and crystallized sub-complexes of the molecular machine responsible for the process and subjected them to X-ray crystallographic analysis. The resulting models clearly show, for the first time, how the hairpin-like conformation of the RNA is altered when it is recognized by the requisite binding proteins in the nucleus. "We were surprised to see that the RNA is not only recognized by these proteins, they also force it to adopt a new form. They staple it together, so to speak," Niessing says. Carriage of the RNAs is the responsibility of so-called motor proteins. With the help of unfolded adaptor proteins, they attach to the RNA-protein complex as it emerges from the nucleus. In doing so, they stabilize the whole assembly, as the structural models demonstrate, thus allowing the RNA to be transported to its destination along the fibers that make up the cytoskeleton, which serve as the system's 'railway lines'.

"The new data represent a major advance in our understanding of the transport of RNA -- a process that is common to all organisms whose cells are nucleated and is vital for their survival."

Comment; Even though this is studied in nucleated cells, the same mechanism had to be present in early life with cells that were not nucleated. All cells have an organized architecture and regulated processes:

http://link.springer.com/article/10.1007/s10539-015-9497-8

"With the central focus of analysis on the case of minimal living systems, we argue that regulation consists in a specific form of second-order control, exerted over the core (constitutive) regime of production and maintenance of the components that actually put together the organism. The main argument is that regulation requires a distinctive architecture of functional relationships, and specifically the action of a dedicated subsystem whose activity is dynamically decoupled from that of the constitutive regime. We distinguish between two major ways in which control mechanisms contribute to the maintenance of a biological organisation in response to internal and external perturbations: dynamic stability and regulation. Based on this distinction an explicit definition and a set of organisational requirements for regulation are provided, and thoroughly illustrated through the examples of bacterial chemotaxis and the lac-operon. The analysis enables us to mark out the differences between regulation and closely related concepts such as feedback, robustness and homeostasis."