Biological complexity: making a ribosome isn't easy (Introduction)

by David Turell @, Saturday, May 23, 2020, 01:36 (10 days ago) @ David Turell

In life the ribosome constructs itself before going to work. It took seven years for humans to do it!:

As the cell's protein factory, the ribosome is the only natural machine that manufactures its own parts. That is why understanding how the machine, itself, is made, could unlock the door to everything from understanding how life develops to designing new methods of drug production.


The core is a long strand of RNA, and 20 different proteins must be attached to the strand. These get organized by the weak chemical forces between the protein molecules and the RNA -- repelling at some points and attracting in others -- and the whole structure thus relies on the proper manufacture and organization of each component. Add to that another six proteins that are not part of the structure, but act as chaperones to assist in the assembly. That makes at total of a least 27 different genes -- one to encode each component or chaperone -- that must work together to make the subunit.


The tiny chips in Bar-Ziv's lab are based on densely-packed DNA strands attached at one end to the surface. In the beginning, the team used all 27 genes needed to reproduce the 30S subunit of a ribosome from an E coli bacterium. The components were caught in "molecular traps" placed near their genes, and this improved the efficiency of the process and enabled the scientists to observe the production process in real time. Then they took a step back, allowing the various parts to autonomously assemble themselves into the ribosomal units, without outside direction or interference. (my bold)


In the beginning, Bar-Ziv and Shulman Daube found they could make the components, but getting them to self-assemble, as the natural structures do, was a challenging hurdle. Over the course of the next seven years and hundreds of trials, the scientists tracked down the proper placement of the genes on the chips. Something like the organization of genes in the chromosome, the genes on the chip had to be positioned in the right locations, and in the proper relative quantities. This, it turned out, was crucial to the overall orchestration of the complex assembly process. Each time, the scientists would attach a different constellation of genes to the chips, narrowing down the possibilities until they had a composition that could mimic that natural process of subunit production as well as self-assembly. In nature, subunit assembly is a hierarchal process. In the course of their experiments, the scientists were able to break down the assembly to the individual steps to prove that the end result was a self-assembled subunit, and to observe the roles of the chaperones in this process. (my bold)

Comment: Note the first bold. One major step was using life's own process rather than humans doing it. And many folks deny it was all designed!

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