Microbial Physiology notes lec6 10-6-10

Microbial Physiology notes lec6 10-6-10 - Microbial Physio...

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Microbial Physio Notes Lecture 6: October 6 2010 Carriers primary active transport and Carriers group translocators -From Carriers to Primary active transport -ABC System = ATP Binding Cassette -the ABC systems are energized by hydrolyzing ATP every time you hydrolyze an ATP, a substrate molecule is transported -the transporters can be either transport uptake of a nutrient or some other molecule into the cell, or depending on the system, they can catalyze efflux from the cell (exporters) -Exporters on the left hand side, and importers on the right hand side are quite similar: -both have a C subunit (cytoplasmic subunit) which is the ATPase that hydrolyzes the ATP and transmits that energy to the carrier which is the membrane incorporated complement which is labeled M -once you have the C and M subunits, the substrate has to bind from the inside and translocated across the membrane as the ATPase hydrolyzes ATP there is no phosphorylation of the protein in this particular type of system -uptake is very similar, you have the C and M subunits in the same configuration, you also have an extracellular receptor that binds the solute and then the conformational change that is induced as a result of substrate binding allows the receptor to bind to the external surface of the M subunit (Membrane integrated channel forming subunit) and then you hydrolyze ATP and substrate is transported across the membrane -ABC transporters use ATP to translocate a variety of compounds across membranes 3 evolutionarily distinct types of membrane proteins: exporters o ABC1 Exporter: o 6TMS protein as alpha helix, but arose from precursor 2TMS hairpin structure that triplicated to give the 6TMSs 2TMSs x 3= 6TMSs o ABC2 Exporter:
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o 6TMS arose from a precursor that only had 3TMS that duplicated to give the 6TMS proteins 3TMSs x 2= 6TMSs o ABC3 Exporter : o 4TMSs x 2= 8TMSs Less common w/ less sequence divergence and with more restricted distribution through out living world don’t find ABC 3 types in higher eukaryotes such as plants, animals, and fungi, but can be found in lower eukaryotes 8TMS proteins arose by duplication of 4TMS o Can find sequence similarity between members of any one of the 3 families( i.e within the ABC 1 family there is sequence similarity in their respective ABC types there is sequence similarity), but there is no significant sequence similarity between the 3 families i.e there is no sequence similarity between the ABC 1, 2, 3 families) therefore we conclude that the 3 types arose independently of each other and possibly at different times throughout evolutionary history All ABC Importers are Derived from ABC2 Exporters o ABC2 was utilized to construct the more complicated uptake system In addition to the C and M subunits also have the extra cytoplasmic receptors 1. Thought that ABC2 exporters were precursors to create uptake system (importer) Basic 6TMS unit has either undergone TMS loss
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This note was uploaded on 01/09/2011 for the course BIMM 130 taught by Professor Saier during the Fall '10 term at UCSD.

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Microbial Physiology notes lec6 10-6-10 - Microbial Physio...

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