Multifaceted stoichiometry control of bacterial operons revealed by data-independent acquisition mass spectrometry

Genes clustered into polycistronic operons was thought a characteristic of bacteria and many other species. More than half protein-coding genes are organized in polycistronic operons composed of two or more than ten genes in bacterial genomes. Although the structure of operons have been studied precisely, how the member genes within operon maintain their stoichiometry expression is remain unknown. Using a highly accurate label-free absolute quantification method DIA (data-independent acquisition), we present a global analysis of Escherichia coli proteome, quantified 1607 proteins, including 59.1% of the known polycistronic operons. We found shorter operons tend to be more tightly controlled than longer operons, and those operons for metabolic pathways are less controlled for stoichiometry balance than those operons for protein complexes. Our results thus reveal the two-level regulation mode involving transcription and translation of operons would balance the stoichiometry expression of genes in polycistronic operons in different time-scale.