Linked transport of phosphate, potassium ions and protons in Escherichia coli.
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ABSTRACT:
SUBMITTER: Russell LM
PROVIDER: S-EPMC1161668 | biostudies-other | 1979 Oct
REPOSITORIES: biostudies-other
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Project description:A series of mutants of Escherichia coli, combining defects in either of the two phosphate transport systems with defects in one or more of the potassium transport systems, was used to study the nature of the previously observed obligatory requirement for each one of these ions in the transport of the other. The results show that no pair of systems is obligatorily linked, and that either ion can be transported by any one of its systems, provided that a means of entry for the other ion is available. Furthermore, in the total absence of Pi, K+ entry accompanies the transport of other anions, such as aspartate, glutamate, sn-glycero-3-phosphate and glucose 6-phosphate. The results indicate that Pi and the other anions enter by symport with protons, and that a simultaneous K+/H+ exchange, which would serve to maintain the intracellular pH, is responsible for the observed K+ 'symport' with these anions.
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Project description:GroEL is a member of the ATP-dependent chaperonin family that promotes the proper folding of many cytosolic bacterial proteins. The structures of GroEL in a variety of different states have been determined using X-ray crystallography and cryo-electron microscopy. In this study, a 3.02 A crystal structure of the native GroEL complex from Escherichia coli is presented. The complex was purified and crystallized in the absence of potassium ions, which allowed evaluation of the structural changes that may occur in response to cognate potassium-ion binding by comparison to the previously determined wild-type GroEL structure (PDB code 1xck), in which potassium ions were observed in all 14 subunits. In general, the structure is similar to the previously determined wild-type GroEL crystal structure with some differences in regard to temperature-factor distribution.
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Project description:1. Addition of L-fucose to energy-depleted anaerobic suspensions of Escherichia coli elicited an uncoupler-sensitive alkaline pH change diagnostic of L-fucose/H+ symport activity. 2. L-Galactose or D-arabinose were also substrates, but not inducers, for the L-fucose/H+ symporter. 3. L-Fucose transport into subcellular vesicles was dependent upon respiration, displayed a pH optimum of about 5.5, and was inhibited by protonophores and ionophores. 4. These results showed that L-fucose transport into E. coli was energized by the transmembrane electrochemical gradient of protons. 5. Neither steady state kinetic measurements nor assays of L-fucose binding to periplasmic proteins revealed the existence of a second L-fucose transport system.
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Project description:Purpose: We use the ribosome profiling protocol to understand why EF4 confers resistance to tellurite and how tellurite affects ribosome. Methods: We used ribosome profiling and transcriptomic data to analyze mainly by plastid software. The ribosome were purified by sucrose gradient separation. Results: Using polysome profile and sequencing data, we found that tellurite disables the ribosome subunits to form a functional 70S ribosome and reduces the ribosome density after tellurite exposure. We also found that tellurite influences the ribosome reaching to stop codon. Tellurite shortened the ribosome protected fragment, this process was mediated by EF4. EF4 mediated more gene expression including these known tellurite resistance genes to confer tellurite resistance. Tellurite also induced many differential gene expression. Conclusions: Tellurite exerts its toxicity on ribosome by disabling 70S ribosome formation, reaching to stop codon, and inducing differential gene expression.
2021-01-29 | GSE109907 | GEO
Project description:Understanding the structure and dynamics of water's constituent ions, proton and hydroxide, has been a subject of numerous experimental and theoretical studies over the last century. Besides their obvious importance in acid-base chemistry, these ions play an important role in numerous applications ranging from enzyme catalysis to environmental chemistry. Despite a long history of research, many fundamental issues regarding their properties continue to be an active area of research. Here, we provide a review of the experimental and theoretical advances made in the last several decades in understanding the structure, dynamics, and transport of the proton and hydroxide ions in different aqueous environments, ranging from water clusters to the bulk liquid and its interfaces with hydrophobic surfaces. The propensity of these ions to accumulate at hydrophobic surfaces has been a subject of intense debate, and we highlight the open issues and challenges in this area. Biological applications reviewed include proton transport along the hydration layer of various membranes and through channel proteins, problems that are at the core of cellular bioenergetics.
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Project description:Escherichia coli is a genetically diverse species infecting hundreds of millions of people worldwide annually. We examined seven well-characterized E. coli pathogens causing urinary tract infections, gastroenteritis, pyelonephritis and haemorrhagic colitis. Their transport proteins were identified and compared with each other and a non-pathogenic E. coli K12 strain to identify transport proteins related to pathogenesis. Each pathogen possesses a unique set of protein secretion systems for export to the cell surface or for injecting effector proteins into host cells. Pathogens have increased numbers of iron siderophore receptors and ABC iron uptake transporters, but the numbers and types of low-affinity secondary iron carriers were uniform in all strains. The presence of outer membrane iron complex receptors and high-affinity ABC iron uptake systems correlated, suggesting co-evolution. Each pathovar encodes a different set of pore-forming toxins and virulence-related outer membrane proteins lacking in K12. Intracellular pathogens proved to have a characteristically distinctive set of nutrient uptake porters, different from those of extracellular pathogens. The results presented in this report provide information about transport systems relevant to various types of E. coli pathogenesis that can be exploited in future basic and applied studies.
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