First single-unit synthetic ribosome opens the door to next-generation synthetic biology

Tying the knot between subunits.  Artist’s impression of conjoined ribosome subunits ERIK CARLSON
Tying the knot between subunits.
Artist’s impression of conjoined ribosome subunits

Researchers from the University of Illinois, Chicago and Northwestern University have engineered the first designer ribosome with artificially tethered subunits, dubbed Ribo-T. The synthetic ribosome works nearly as well as its original cellular counterpart and may not only be used for exploring hitherto poorly understood functions of the ribosome, but could eventually have applications in next-generation synthetic biology.

Ribosomes are fundamental molecular machines that churn out proteins within the cell, and comprises of two independent subunits built on their own ribosomal RNA (rRNA) scaffolds. The established model of protein synthesis has the two subunits uniting on a single messenger RNA (mRNA) read-out for every cycle of protein synthesis, and working in a concerted assembly to translate proteins, followed by their dissociation into separate entities. This free exchange of subunits for every protein synthesis cycle was thought to be essential to the ribosome’s function since it’s evolutionarily conserved throughout all kingdoms of life.

However in this study, scientists stitched the two subunits together using their rRNA scaffolds to generate a tethered ribosome they called Ribo-T. This was a painstaking and iterative process that required several permutations to identify and generate a chimaeric rRNA molecule that would not interfere with the regular ribosomal functions and yet function orthogonally. The months of work paid off in surprising results, where the tethered ribosome maintained and supported the growth of Escherichia coli cells that lacked their own RNA. To further tweak the system, researchers Malkin and Jewett modified the Ribo-T to recognize only certain mRNAs with a specific signal sequence, thereby generating a fully orthogonal translation system.

The orthogonal nature of the Ribo-T paves the way to altering the prime center of the ribosome activity at its catalytic core, giving rise to interesting prospects in the field of synthetic biology.

“Our new protein-making factory holds promise to expand the genetic code in a unique and transformative way, providing exciting opportunities for synthetic biology and biomolecular engineering,” Jewett said.

“This is an exciting tool to explore ribosomal functions by experimenting with the most critical parts of the protein synthesis machine, which previously were ‘untouchable,’” Mankin added.

Source: The Scientist

Original Article : Nature