Abstract
More than half of the protein-coding genes in bacteria are organized in polycistronic operons composed of two or more genes. It remains under debate whether the operon organization maintains the stoichiometric expression of the genes within an operon. In this study, we performed a label-free data-independent acquisition hyper reaction monitoring mass-spectrometry (HRM-MS) experiment to quantify the Escherichia coli proteome in exponential phase and quantified 93.6% of the cytosolic proteins, covering 67.9% and 56.0% of the translating polycistronic operons in BW25113 and MG1655 strains, respectively. We found that the translational regulation contributes largely to the proteome complexity: the shorter operons tend to be more tightly controlled for stoichiometry than longer operons; the operons which mainly code for complexes is more tightly controlled for stoichiometry than the operons which mainly code for metabolic pathways. The gene interval (distance between adjacent genes in one operon) may serve as a regulatory factor for stoichiometry. The catalytic efficiency might be a driving force for differential expression of enzymes encoded in one operon. These results illustrated the multifaceted nature of the operon regulation: the operon unified transcriptional level and gene-specific translational level. This multi-level regulation benefits the host by optimizing the efficiency of the productivity of metabolic pathways and maintenance of different types of protein complexes.
Highlights
An operon is a cluster of genes transcribed in a single mRNA
Escherichia coli K-12 sub-strains BW25113 and MG1655 were cultivated on glucose M9 minimal medium at 37◦C in flasks to mid-exponential phase (OD600 = 0.6) and harvested in 45 mL volume, immediately cooled in ice water, and centrifuged at 10,000 × g for 5 min
We examined if the number of genes per operon could affect the stoichiometry of proteins encoded within operons in both BW25113 and MG1655 strains
Summary
An operon is a cluster of genes transcribed in a single mRNA. This principle is conserved across bacterial and archaeal genomes, as well as mitochondria and chloroplast (Wolf et al, 2001; Price et al, 2005; Zheng et al, 2005). In a typical bacterial genome, more than half of the protein-coding genes are organized in multigene operons. A classical bacterial operon generates an mRNA strand with polycistronic structure containing multiple coding sequences and are translated together in the cytoplasm. These genes are often of related functions, for example, to build a protein
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
