A research group examining how bacteria cope with stress, for example how the receptor meolecule CadC monitors the acidity in the environment and alerts the cell to take countermeasures to protect itself, led to some answers about protein synthesis, the core biosynthetic process that makes all metabolism possible.
They found that, in the absence of Translation Elongation Factor P (EF-P, for short), the cell doesn't make enough CadC to carry out its job effectively.
How does EF-P regulate protein synthesis in general, and the synthesis of CadC in particular? Ribosomes translate the genetic blueprints for proteins into the correct sequence of amino acids as they move along a messenger RNA molecule. But when the blueprint calls for the addition of several successive proline amino acids onto the growing protein chain, the ribosomes grind to a halt.
It turns out that EF-P is required to get these stalled ribosomes going again. Moreover, the factor not only fulfills this function in bacteria and in archaea, but also in the cells of eukaryotic organisms, which have their own versions of EF-P.
The researchers believe that the translation stop imposed by a short run of prolines provides a means of adjusting protein copy numbers in response to changing conditions.
In bacteria, a functionally diverse set of around 100 proteins is known to contain such proline-rich motifs. This suggests that the stalling phenomenon indeed has a more general regulatory role, and may even provide a target for new antibiotics.
One of the researchers, Daniel Wilson of Ludwig-Maximilians-Universität in Munich, recently discovered the last enzyme in the EF-P modification pathway: For its rescue activity, the factor must be modified by other enzymes – which are not found in humans.