Expression,Purification,and Preliminary Characterization Of Potassium Ion Transporters In Escherichia Coli

Ions play a vital role in the biological processes of organisms and are an indispensable component of life,among which potassium is an essential element.In bacteria,potassium is the most abundant ion in the cytoplasm.Potassium uptake and release are involved in osmotic regulation,p H homeostasis,regulation of protein synthesis,enzyme activation,membrane potential adjustment,electrical signaling,and virulence regulation.For these purposes,bacteria have evolved a range of different potassium ion transport proteins.Some are passive channels that allow potassium ions to flow along their electrochemical gradient without expending energy,while others are active transporters that use ATP or proton motive force to move potassium ions against their electrochemical gradient.Each transport system has different molecular properties that affect the response or production of proteins to stimuli,including conductance and transport rates,opening probability,and ligand activation or deactivation.The actions of these different proteins combine to establish the membrane physiology of bacteria.In this paper,the potassium transport proteins of Escherichia coli were taken as the research objects.The information of potassium transport proteins in Escherichia coli was collected through literature and database.And potassium transporter samples suitable for subsequent characterization were obtained by constructing expression plasmid,screening overexpressed protein,screening suitable purification detergent,Ni-NTA affinity chromatography and gel filtration chromatography.Then using negative staining technique and Cryo-EM to preliminarily characterize the potassium transport proteins,and the structure analysis of Kch,Kdp D and Nha P2 has been preliminary explored.The purpose of this study is to establish the process and technical means for the construction,expression,purification,characterization and screening of transport proteins in our laboratory,and to screen out in vitro recombinant potassium ion proteins with high expression characteristics for further research.This study provides a foundation for further study of potassium ion transporters in bacteria,and is also conducive to the study of the structure function and ion transport mechanism of homologous proteins in eukaryotes,and lays a certain research foundation for further screening of more transporters and structural analysis by cryo-electron microscopy.The study of potassium transport proteins is an important basis for understanding their physiological contribution and regulation,which is of great significance not only in the study of biological mechanism but also in the application of agriculture,animal husbandry and medicine.