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Center for Nonlinear Studies |
I will talk about a project I worked on this past summer at the Weizmann Institute of Science. There I studied the distribution of protein number and promoter activity of E. coli in three different environmental conditions. This work was mainly motivated by a recent paper on E. coli's metabolic network, which argues that its node degree distribution is scale-rich (as opposed to scale-free) and that it's high variability is due to the high degree of metabolites, which act as "knots" in the bow-tie structure of metabolism (R. Tanaka, Scale-Rich Metabolic Networks. Physical Review Letters 94 168101 (2005)). Trying to give a similar twist to the protein distribution story, we found that, across all three conditions, many of the most highly expressed proteins are ribosomal, “knots” in the transcription and translation bow-tie. However, we also found that the high-variability of the distribution is not entirely due to these proteins. Finally, partitioning the distribution into different protein classes, each class with a different function, does not fit a scale-rich picture.