Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane. Peripheral membrane proteins are transiently associated with the cell membrane.
A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently undergo significant conformational changes to move a substance through the membrane. They are usually highly hydrophobic and aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.
PEP group translocation, also known as the phosphotransferase system or PTS, is a distinct method used by bacteria for sugar uptake where the source of energy is from phosphoenolpyruvate (PEP). It is known to be a multicomponent system that always involves enzymes of the plasma membrane and those in the cytoplasm.
The ABC transporters, ATP synthase (ATP)-binding cassette transporters are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to humans. ABC transporters belong to translocases.
The bacterial outer membrane is found in gram-negative bacteria. Gram-negative bacteria form two lipid bilayers in their cell envelopes - an inner membrane (IM) that encapsulates the cytoplasm, and an outer membrane (OM) that encapsulates the periplasm.
An efflux pump is an active transporter in cells that moves out unwanted material. Efflux pumps are an important component in bacteria in their ability to remove antibiotics. The efflux could also be the movement of heavy metals, organic pollutants, plant-produced compounds, quorum sensing signals, bacterial metabolites and neurotransmitters. All microorganisms, with a few exceptions, have highly conserved DNA sequences in their genome that encode efflux pumps. Efflux pumps actively move substances out of a microorganism, in a process known as active efflux, which is a vital part of xenobiotic metabolism. This active efflux mechanism is responsible for various types of resistance to bacterial pathogens within bacterial species - the most concerning being antibiotic resistance because microorganisms can have adapted efflux pumps to divert toxins out of the cytoplasm and into extracellular media.
A colicin is a type of bacteriocin produced by and toxic to some strains of Escherichia coli. Colicins are released into the environment to reduce competition from other bacterial strains. Colicins bind to outer membrane receptors, using them to translocate to the cytoplasm or cytoplasmic membrane, where they exert their cytotoxic effect, including depolarisation of the cytoplasmic membrane, DNase activity, RNase activity, or inhibition of murein synthesis.
David S. Cafiso is an American biochemist and a professor of chemistry at the University of Virginia. His research focuses on membrane proteins and cell signaling, and is primarily supported by grants from the National Institute of Health.
In enzymology, an iron-chelate-transporting ATPase (EC 3.6.3.34) is an enzyme that catalyzes the chemical reaction
In enzymology, a maltose-transporting ATPase (EC 3.6.3.19) is an enzyme that catalyzes the chemical reaction
In enzymology, a phosphate-transporting ATPase (EC 3.6.3.27) is an enzyme that catalyzes the chemical reaction
In enzymology, a polyamine-transporting ATPase (EC 3.6.3.31) is an enzyme that catalyzes the chemical reaction
In enzymology, a vitamin B12-transporting ATPase (EC 3.6.3.33) is an enzyme that catalyzes the chemical reaction
Escherichia virus T5, sometimes called Bacteriophage T5 is a caudal virus within the family Demerecviridae. This bacteriophage specifically infects E. coli bacterial cells and follows a lytic life cycle.
The sodium/glutamate symporter, also known as glutamate permease, is a transmembrane protein family found in bacteria and archaea. These proteins are symporters that are responsible for the sodium-dependent uptake of extracellular glutamate into the cell. They are integral membrane proteins located in the bacterial inner membrane. The best-studied member of the family is GltS from Escherichia coli. GltS contains ten transmembrane helices arranged in two antiparallel 5-helix domains and functions as a homodimer. Substrates for GltS include L- and D-glutamate, as well as toxic analogs α-methylglutamate, and homocysteate. In studies of E. coli growth, bacteria without GltS were unable to grow in a medium where glutamate is the only source of carbon.
Ammonia transporters are structurally related membrane transport proteins called Amt proteins in bacteria and plants, methylammonium/ammonium permeases (MEPs) in yeast, or Rhesus (Rh) proteins in chordates. In humans, the RhAG, RhBG, and RhCG Rhesus proteins constitute solute carrier family 42 whilst RhD and RhCE form the Rh blood group system. The three-dimensional structure of the ammonia transport protein AmtB from Escherichia coli has been determined by x-ray crystallography revealing a hydrophobic ammonia channel. The human RhCG ammonia transporter was found to have a similar ammonia-conducting channel structure. It was proposed that the erythrocyte Rh complex is a heterotrimer of RhAG, RhD, and RhCE subunits in which RhD and RhCE might play roles in anchoring the ammonia-conducting RhAG subunit to the cytoskeleton. Based on reconstitution experiments, purified RhCG subunits alone can function to transport ammonia. RhCG is required for normal acid excretion by the mouse kidney and epididymis.
Many bacteria secrete small iron-binding molecules called siderophores, which bind strongly to ferric ions. FepA is an integral bacterial outer membrane porin protein that belongs to outer membrane receptor family and provides the active transport of iron bound by the siderophore enterobactin from the extracellular space, into the periplasm of Gram-negative bacteria. FepA has also been shown to transport vitamin B12, and colicins B and D as well. This protein belongs to family of ligand-gated protein channels.
Escherichia virus H8 is a bacteriophage known to infect bacterial species of the genus Escherichia and the related genus Salmonella. Its shape and genome are similar to that of Bacteriophage T5.
The p-aminobenzoyl-glutamate transporter(AbgT) family (TC# 2.A.68) is a family of transporter proteins belonging to the ion transporter (IT) superfamily. The AbgT family consists of the AbgT (YdaH; TC# 2.A.68.1.1) protein of E. coli and the MtrF drug exporter (TC# 2.A.68.1.2) of Neisseria gonorrhoeae. The former protein is apparently cryptic in wild-type cells, but when expressed on a high copy number plasmid, or when expressed at higher levels due to mutation, it appeared to allow uptake (Km = 123 nM; see Michaelis–Menten kinetics) and subsequent utilization of p-aminobenzoyl-glutamate as a source of p-aminobenzoate for p-aminobenzoate auxotrophs. p-Aminobenzoate is a constituent of and a precursor for the biosynthesis of folic acid. MtrF was annotated as a putative drug efflux pump.
The C4-dicarboxylate uptake family or Dcu family is a family of transmembrane ion transporters found in bacteria. Their function is to exchange dicarboxylates such as aspartate, malate, fumarate and succinate.
