Can a large manufacturing plant save money by studying a tiny ribosome? For any company in such a business, energy costs are critical to the bottom line. If someone could design manufacturing equipment that derived energy for some of its most critical steps from the ambient temperature in the manufacturing facility––a comfortable temperature for the equipment and the workers––their expertise would be in high demand. That’s essentially what the ribosome does when it uses Brownian motion to fuel many of the steps in the process of translation,1 because the temperature at which the cell is maintained is the source of the thermal energy that results in Brownian motion.
The reason this critical function, translation, can be partly powered by Brownian motion is that the molecules central to translation––ribosomal RNA (rRNA), messenger RNA (mRNA) and transfer RNA (tRNA)––are held into their functional shape through hydrogen bonds and the bonds between the molecules are hydrogen bonds. In general, hydrogen bonds are much weaker than most bonds that connect the atoms in a molecule. The total strength of all the hydrogen bonds in an RNA molecule is high, but in a small area the strength of the hydrogen bonds is relatively weak.
Hydrogen bonds are critical to three distinct aspects of the translation process. First, hydrogen bonding is used to select the correct amino acid to add to the protein chain based on hydrogen bonding between the mRNA codon and the tRNA anticodon––a full complement of hydrogen bonds can only be formed if the tRNA is the one that carries the correct amino acid dictated in the genetic code for the particular codon in the mRNA. Second, formation of the correct codonanticodon hydrogen bonds triggers breaking of hydrogen bonds in some areas of rRNA, rearrangement of the overall structure of the RNA, and formation of new hydrogen bonds to hold the rearranged structure in place. Third, a rearrangement of the tRNA structure occurs, which moves the amino acid attached to the tRNA into position so that a bond can be formed between this amino acid and the protein chain. Later, after the new amino acid is added to the protein chain, the codon-anticodon bonds must be broken (releasing the tRNA) and the rRNA must revert to its original structure in order to accommodate the next codon in the mRNA. These resetting steps also require the breaking of hydrogen bonds and the formation of new hydrogen bonds.
Scientists are just beginning to understand how cellular processes like translation take advantage of Brownian motion to power critical functions of the cell. Making progress in these areas requires using multiple cutting-edge techniques to collect data and keen intellect and insight to correctly interpret the data. As scientists gain insight, they are increasingly awed by the subtlety and beauty of design at the molecular level. If we could emulate the ribosome, we could translate the process of translation into manufacturing energy efficiency and substantial cost savings.
Dr. Patricia Fanning
Patricia Fanning is an RNA biochemist with a PhD from North Carolina State University and formerly a consultant for software companies. As a visiting scholar to Reasons To Believe in 2011, she specialized in human embryology and evolutionary development and regularly contributed to RTB’s podcasts and publications.
- Joachim Frank and Ruben L. Gonzalez Jr., “Structure and Dynamics of a Processive Brownian Motor: The Translating Ribosome,” Annual Reviews in Biochemistry 79 (2010): 381–412.