Modelling efficiency, error propagation and the effect of error-enhancing drugs in protein synthesis.

The efficiency of protein synthesis is discussed with the main emphasis on the accuracy. The error increase by erroneous synthesizing proteins is studied by a theoretical model which includes the coupling of the amino acylation step to the protein synthesis at the ribosomes. Depending on parameter values, the model yields a stable point of relatively high accuracy, a point where most of the accuracy is lost and virtually no functioning proteins are produced (error catastrophe), or both. The effect of an error enhancing drug such as streptomycin can be considered, and it is found that one can have a situation where small amounts of the drug yields a decreased but stable accuracy, and where this possibility disappears at a certain drug level. At higher drug levels, the cells cannot attain any accuracy. The transition is quite drastic, and analogous to a phase transition.