The Significance And Possible Mechanism Of Multifaceted Stoichiometry Control Of Bacterial Operons

An operon composed of two or more genes,is a cluster of genes transcribed in a single mRNA.Operons are also found in virus,bacterial and some lower eukaryotes.In a typical bacterial genome,more than half of the protein-coding genes are organized in multigene operons.These genes are often of related functions,for example,to build a protein complex or to participate in one metabolic pathway.It remains under debate whether the operon organization maintains the stoichiometric expression of the genes within an operon.In this study,we performed RNA-seq,Ribo-seq and hyper reaction monitoring mass-spectrometry(HRM-MS)experiment to quantify the Escherichia coli gene in exponential phase.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.