Energy Cost for Protein Synthesis

Ludwig-Maximilians-Universitaet (LMU) in Munich researchers have elucidated a mechanism that recycles bacterial ribosomes stalled on messenger RNAs that lack termination codons. The protein involved provides a potential target for future antibiotics.

Binding of tRNA to Ribosome: 1 GTP

HHMI scientists and their colleagues discover a new mechanism of protein synthesis.

Protein biosynthesis - Wikipedia

Ribosomes are the cell’s molecular machines, responsible for translating genetic information in messenger RNA into the long strings of amino acids needed to build new proteins. A central tenet of biology has long held that each amino acid added to a peptide chain is specified by an RNA message as it threads its way through the ribosome. But Howard Hughes Medical Institute (HHMI) scientists and their colleagues at UCSF and Stanford have discovered that this is not always true.

Ribosomes and Protein Synthesis | Biology I

The new research has uncovered a new mechanism by which ribosomes can synthesize proteins. The studies show that a protein involved in the cell's ribosome quality control system mediates the elongation of peptides that become stalled during protein sysnthesis. Surprisingly, it does this in the absence of both messenger RNA and the ribosome's small, message-reading subunit.

Mitochondrial ribosomes are comprised of a large subunit, 16S rRNA and a small subunit 12S rRNA.

DNA and Protein Synthesis - BioTopics Website

The ribosome is a large molecular complex of RNA and protein. When eukaryotic ribosomes are isolated from cell extracts, two different fractions are obtained, representing two subunits. The smaller 40S subunit binds the messenger RNA that constitutes the protein's genetic blueprint, as well as the transfer RNA that carries each specific amino acid to be added to the growing chainlike protein molecule. The larger 60S subunit catalyzes the formation of the bond between each amino acid and the growing protein chain.

Protein Synthesis and Ribosome Structure: ..

Together, the evidence was convincing. “What all of this was saying was that we were getting a totally unprecedented mechanism for ribosome-mediated protein synthesis,” Weissman says. “Every other time that people have seen the ribosome make or extend proteins, it's been a messenger RNA that's responsible for bringing the tRNA to read out the genetic code, and you need a large and a small subunit. Here we had synthesis with no messenger RNA and no small subunit. And a protein, Rqc2, was responsible for recognizing and recruiting these specific tRNAs.”

dna rna and protein synthesis | Rna | Ribosome - Scribd

New technology and better computational techniques allowed the team to refine its images, until it became clear that there was indeed a tRNA molecule sitting in that cavity, which is known as the ribosome's A site.“That was very strange because we thought all protein synthesis had ended. The small subunit had gone away; the mRNA had gone away. We thought the ribosome was completely in destruction mode. So why was it bringing in a tRNA with an amino acid ready to be added on to the nascent chain?” Weissman says.

SparkNotes: SAT Subject Test: Biology: Protein Synthesis

The new discovery, the scientists say, was serendipitous. The team initially sought to better understand a quality control complex that Weissman and Brandman discovered in 2012, when Brandman was a postdoctoral researcher in Weissman's lab. The Ribosome Quality Control Complex (RQC) recognizes and destroys incomplete proteins that protrude from large ribosomal subunits that become detached from the rest of the ribosome when protein translation stalls.

DNA Replication and Protein Synthesis - PBS

“We initially just kind of scratched our heads. It wasn't clear to us why the A site would be occupied by a tRNA, or even how,” Frost says. The team wondered about the identity of the tRNAs: Could any of the cell's tRNAs enter the A site after it had been separated from the genetic message and the rest of the ribosome? Or did specific tRNAs arrive with specific amino acids? Collaborating with Alan Lambowitz at the University of Texas, Austin, they found that only tRNAs carrying the amino acids alanine or threonine were present in the complex.