Rao:Translation

In recent years, an increased emphasis has been placed on the use of mathematical models to understand complex cellular processes. One of the challenges in developing these models is that kinetic parameters are often difficult to obtain from experimental measurements or infer from genome sequences. One such challenge is the need to determine protein concentrations from mRNA concentrations. The latter can be easily measured using DNA microarrays or quantitative PCR, whereas direct measurement of the former is far more difficult. Developing simple correlations between mRNA and protein concentration is also limited by the fact that multiple proteins are often synthesized from the same mRNA strand in prokaryotes.

The operon is the fundamental transcriptional unit in bacteria. In the most general terms, an operon is a collection of genes transcribed on the same mRNA strand. Typically, the genes within an operon are associated with common cellular processes such as a metabolic pathway. It has been observed experimentally that the numbers of the proteins expressed from a given operon are not equal. For example, in the meche operon in E. coli, the numbers vary from a few hundred to almost twenty thousand. Developing predictive models for bacterial cellular processes requires a detailed knowledge of the stoichiometry of the protein components within an operon. Moreover, having predictive capability for protein expression in operons will allow novel, non-native cellular processes to be introduced into bacterial hosts, allowing for applications in pharmaceutical and biochemical production.