This site features trending ABC Transporters-linked items from the web for 5 of August 2019.
Trending ABC Transporters news item:
Protein dynamics: Molecular machines at work Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich have used a special fluorescence-based imaging technique to track the shape changes that occur when pore proteins in the cell membrane export molecules into the extracellular medium. A biological cell can be thought of as a hive, in which proteins play the role of the worker bees. However, proteins are far more versatile and can interact with each other to form molecular machines. In order to understand the mechanisms that underlie their functional versatility, structural biologists have relied primarily on the analysis of their three-dimensional structures following crystallization… read the entire news item (from Science Daily)
Featured recent scientific publication on ABC Transporters:
Powering the ABC multidrug exporter LmrA: How nucleotides embrace the ion-motive force LmrA is a bacterial ATP-binding cassette (ABC) multidrug exporter that uses metabolic energy to transport ions, cytotoxic drugs, and lipids. Voltage clamping in a Port-a-Patch was used to monitor electrical currents associated with the transport of monovalent cationic HEPES+ by single-LmrA transporters and ensembles of transporters. In these experiments, one proton and one chloride ion are effluxed together with each HEPES+ ion out of the inner compartment, whereas two sodium ions are transported into this compartment. Consequently, the sodium-motive force (interior negative and low) can drive this electrogenic ion exchange mechanism in cells under physiological conditions. The same mechanism is also relevant for the efflux of monovalent cationic ethidium, a typical multidrug transporter substrate. Studies in the presence of Mg-ATP (adenosine 5′-triphosphate) show that ion-coupled HEPES+ transport is associated with ATP-bound LmrA, whereas ion-coupled ethidium transport requires ATP binding and hydrolysis. HEPES+ is highly soluble in a water-based environment, whereas ethidium has a strong preference for residence in the water-repelling plasma membrane. We conclude that the mechanism of the ABC transporter LmrA is fundamentally related to that of an ion antiporter that uses extra steps (ATP binding and hydrolysis) to retrieve and transport membrane-soluble substrates from the phospholipid bilayer… read the entire scientific publication (from Science Advances)
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Background knowledge on ABC Transporters:
ABC Transporters The ABC proteins constitute the largest family of proteins.They are present in all living species from Archaea to Homo sapiens. They make up to 4% of the full genome complement of bacteria such as Escherichia coli or Bacillus subtilis. Eacheukaryote genome contains several dozens of members (over 100 in the plant Arabidopsis thaliana). They are recognized by a consensus ATP-binding region of approximately 100 amino acids which include the two Walker A and B motifs encompassing a linker or C region (Figure 1). The ABC proteins catalyze a wide variety of physiological functions,most (but not all) of which being related to transport. This article describes the major physiological and biochemical functions as well as the structural properties of some of the best-known ABC transporters using examples from the yeast Saccharomyces cerevisiae and Homo sapiens. Topology:Most, but not all, ABC proteins are ABC transporters. Each of those molecules contains, or is associated to, oneor two cytoplasmic ATP-binding domains named nucleotide binding domains (NBDs) (Figure 1) and one or two transmembrane domains (TMDs) (Figure 2). Each TMD comprises usually six a-helix spans. Association of one TMD to one NBD results in a half-size ABC transporter;however, they are believed to function as homo- orheterodimers so that the minimal functional organization of an ABC transporter is considered to be TMD–NBD–TMD–NBD or NBD–TMD–NBD–TMD. In eukaryotes, two TMDs and two NBDs are often associated in one single molecule called full-sized ABC transporter.The topological relation between NBD(s) and TMDs is variable (Figure 2). In bacteria two NBDs often associate with two TMDs either as four single subunits encoded by the same operon or in various combinations of fused subunits. Association of other proteins may occur. The most prominent associated bacterial protein is the periplasmic solute-binding receptor, which in gram-negative bacteria is found in the periplasm, and in gram-positive bacteria is present often as a lipoprotein, bound to the external membrane surface via electrostatic interactions (Figure 3)… read more (from Encyclopedia of Biological Chemistry, 1st Edition)
Keywords: ABC Transporters, #ABCB1, transmembrane domains (TMDs), the ABC multidrug exporter LmrA.
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