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Topic: Allosteric

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	Energy, Enzymes, and Catalysis Problem Set (Site not responding. Last check: 2007-09-06)
		Allosteric enzymes change shape between active and inactive shapes as a result of the binding of substrates at the active site, and of regulatory molecules at other sites.
		In the simple case of an allosteric enzyme with an active and inactive form, the change in reaction rate with increasing substrate concentration is typically an "S-shaped" curve.
		Allosteric enzymes are used by cells to regulate metabolic pathways where the concentration of cellular substrates fluxuate over narrow concentration ranges.
	www.biology.arizona.edu /biochemistry/problem_sets/energy_enzymes_catalysis/14t.html (277 words)

	Enzyme Regulation
		Allosteric regulation: regulation of enzyme activity through the binding of allosteric effectors that either activate (positive effectors) or inhibit (negative effectors) the activity of the enzyme:
		Enz1 is an allosteric enzyme, and Ile is a negative allosteric effector for enz1; also called a feedback inhibitor.
		Allosteric regulation is achieved through noncovalent interactions (binding) of substrates and effectors to the enzyme.
	www.people.virginia.edu /~rjh9u/IntroBio/bio201/lectures/Lecture14.html (456 words)

	Molecular Interactions in Cell Events: Catalysis : Control of enzyme activity : Allosteric enzymes
		Allosteric enzymes change their conformation in response to the binding of a regulating molecule.
		Allosteric enzymes have two conformations, one that is active, catalytically, and the other that is inactive.
		The principle of allosteric control of enzyme activity is illustrated in Figure 13.
	scholar.hw.ac.uk /site/biology/topic11.asp?outline= (202 words)

	Energy, Enzymes, and Catalysis Problem Set
		Allosteric enzymes may also have regulatory subunits that bind either activators or inhibitors.
		Inhibitors cause the allosteric enzyme to adopt the inactive shape.
		The binding of an allosteric inhibitor causes the enzyme to adopt the inactive conformation, and promotes the cooperative binding of a second inhibitor.
	www.biology.arizona.edu /biochemistry/problem_sets/energy_enzymes_catalysis/03t.html (343 words)

	Ligand Binding Problems (Single site, non-cooperative) (Site not responding. Last check: 2007-09-06)
		Allosteric effects occur when the binding properties of a macromolecule change as a consequence of a second ligand binding to the macromolecule and altering its affinity towards the first, or primary, ligand.
		Allosteric effects are important in the regulation of enzymatic reactions.
		The allosteric effector stabilizes the tense state, or lowers its energy relative to that of the relaxed state.
	stingray.bio.cmu.edu /~web/bc/Lec/Lec13/lec13.html (695 words)

	Allosteric Regulation of Catalytic Activity: Escherichia coli Aspartate Transcarbamoylase versus Yeast Chorismate ...
		The residues which change their position during allosteric transition and thereby transduce the signal of effector binding from the allosteric to the active site are shown as stick models (green, carbon; blue, nitrogen; red, oxygen).
		Carbamyl phosphate: an allosteric substrate for aspartate transcarbamylase of Escherichia coli.
		The pAR5 mutation and the allosteric mechanism of Escherichia coli aspartate carbamoyltransferase.
	mmbr.asm.org /cgi/content/full/65/3/404 (10351 words)

	enzymes-part II
		Allosteric enzymes are "co-operative" systems,in which a small change in one parameter, e.g.
		Allosteric effectors bring about catalytic modification by binding to the enzyme at distinct allosteric sites, well removed from the catalytic site, and causing conformational changes that are transmitted through the bulk of the protein to the catalytically active site(s).
		Most allosteric enzymes are oligomeric (consisting of multiple subunits); generally they are located at or near branch points in metabolic pathways, where they are influential in directing substrates along one or another of the available metabolic paths.
	www.med.unibs.it /~marchesi/enzymes2.html (1656 words)

	Allosteric Site on Muscarinic Acetylcholine Receptors: A Single Amino Acid in Transmembrane Region 7 Is Critical to the ...
		of the allosteric ligand at the NMS-occupied receptor (Lazareno
		for allosteric ligands at the free and NMS-liganded receptors
		Leppik RA, Miller RC, Eck M and Paquet JL (1994) Role of acidic amino acids in the allosteric modulation by gallamine of antagonist binding at the m2 muscarinic acetylcholine receptor.
	molpharm.aspetjournals.org /cgi/content/full/61/1/160 (4649 words)

	ALLOSTERIC ENZYMES (Site not responding. Last check: 2007-09-06)
		Yeast hexokinase, an allosteric dimer with non equivalent monomers.
		Mamalian phosphofructokinase, structure and allosteric properties, effect of AMP and ATP.
		Allosteric and hormonal control of Fructose bisphosphatase in liver.
	www-esbs.u-strasbg.fr /courses/enz2.htm (79 words)

	Jean Pierre Changeux and Molecular Neurobiology, History
		It is fair to mention however that the two-state scheme is still challenged, today, by the « induced fit » or sequential model of Koshland, Némethy and Filmer (1966) according to which the protein molecule « adapts » its shape to the structure of the particular ligand bound through multiple and variable conformational states.
		The initial theory on allosteric proteins, as formulated in 1963, was designed for regulatory enzymes but included references to gene repressors and to hormone receptors.
		Allosteric transitions of the acetylcholine receptor: the molecular mechanism of desensitization (1972-1983)
	www.pasteur.fr /recherche/unites/neubiomol/history.html (8987 words)

	A to H
		An allosteric enzyme is an enzyme that contains a region to which small, regulatory molecules ("effectors") may bind in addition to and separate from the substrate binding site and thereby affect the catalytic activity.
		On binding the effector, the catalytic activity of the enzyme towards the substrate may be enhanced, in which case the effector is an activator, or reduced, in which case it is a de-activator or inhibitor.
		Allosteric regulation is the regulation of the activity of allosteric enzymes.
	www.chem.qmul.ac.uk /iupac/medchem/ah.html (2005 words)

	KUMC Aron Fenton, PhD (Site not responding. Last check: 2007-09-06)
		At the single protein level, allosteric regulation is the altered functions that result when a regulatory molecule binds to a protein at a site distinct from the protein’ s active site.
		Pyruvate kinase from human liver (L-PYK) is allosterically activated by Fru-1,6-BP and allosterically inhibited by ATP and Ala.
		Instead of limiting our thoughts to a limited number of assumed confirmations, we consider allosteric regulation using thermodynamic arguments that are free of presumed conformational states.
	www.kumc.edu /biochemistry/Fenton.html (496 words)

	Allosteric Modulators: The New Generation of Receptor Antagonist -- Kenakin 4 (4): 222 -- Molecular Interventions
		an indicatior of "efficacy" of an allosteric antagonist; the
		873140 is a synthetic small-molecule (0.6 kDa) non-competitive allosteric antagonist.
		Both allosteric and orthosteric antagonists can manifest identical behaviors, such as parallel shifts of dose-response curves (with no diminution of maxima) for simple competitive antagonists, depression of maximal response with no shift to the right for noncompetitive antagonists, and sigmoid binding curves (with complete displacement of radioligand).
	molinterv.aspetjournals.org /cgi/content/full/4/4/222 (3444 words)

	Are the Common Allosteric Models Correct?
		For our purposes, allosteric refers to the regulation (either inhibition or activation) of enzyme activity due to the binding of a metabolite to a site on the enzyme that is different from the active site.
		An allosteric inhibitor binds to an allosteric site and shifts the conformational equilibrium to one that is relatively inactive.
		The purpose of the experiment is to determine if the individual allosteric sites (x-axis) have an effect on the bonding of a specific active site.
	www.angelfire.com /falcon/cheesehead/reinhart.html (852 words)

	Allosteric Enhancers of A1 Adenosine Receptors Increase Receptor-G Protein Coupling and Counteract Guanine Nucleotide ...
		Kourounakis A, Visser C, de Groote M and IJzerman AP (2001) differential effects of the allosteric enhancer (2-amino-4,5-dimethyl-trienyl)[3-(trifluoromethyl) phenyl-]methanone (PD81,723) on agonist and antagonist binding and function at the human wild-type and a mutant (T277A) adenosine A(1) receptor.
		Lutjens H, Zickgraf A, Figler H, Linden J, Olsson RA, and Scammells PJ (2003) 2-Amino-3-benzoylthiophene allosteric enhancers of A(1) adenosine agonist binding: new 3,4- and 5-modifications.
		Mizumura T, Auchampach JA, Linden J, Bruns RF, and Gross GJ (1996) PD 81,723, an allosteric enhancer of the A1 adenosine receptor, lowers the threshold for ischemic preconditioning in dogs.
	molpharm.aspetjournals.org /cgi/content/full/64/6/1557 (4233 words)

	[No title] (Site not responding. Last check: 2007-09-06)
		The allosteric enzyme is a dimer with identical subunits so it is called a homodimer (A-A, where 'A' represents one of the identical subunits).
		Thus, the influence of the allosteric modifier must be transmitted through the framework of the enzyme in order to influence the activity of the enzyme - either positively or negatively.
		Then, when the positive allosteric modifier is present, the enzyme is altered in shape, usually both subunits change shape and the dimer takes on a new conformation.
	www.bio.mtu.edu /campbell/401lec17p2.html (634 words)

	Our Science: Aptamers and Allosteric Ribozymes
		Allosteric ribozymes are RNA enzymes whose activity is modulated by the binding of an effector molecule to an aptamer domain, which is located apart from the active site.
		Allosteric selections link the evolution of the new aptamer to ribozyme function.
		These allosteric RNAs can be immobilized as biosensors in an array format to report the presence of analytes in complex biological mixtures.
	www.yale.edu /breaker/aptamer-allostery.htm (228 words)

	Combined Allosteric and Competitive Interaction between Extracellular Na+ and K+ During Ion Transport by the alpha 1, ...
		Combined Allosteric and Competitive Interaction between Extracellular Na+ and K+ During Ion Transport by the alpha 1, alpha 2, and alpha 3 Isoforms of the Na, K-ATPase -- Balshaw et al.
		A combined allosteric and competitive model describes the interaction between extracellular Na and Rb during ion transport mediated by the Na, K-ATPase.
		significance of the increased affinity for Rb and decreased affinity for allosteric Na observed for the
	www.biophysj.org /cgi/content/full/79/2/853 (4661 words)

	Allosteric transition pathways in the lactose repressor protein core domains: Asymmetric motions in a homodimer -- ...
		Allosteric transition pathways in the lactose repressor protein core domains: Asymmetric motions in a homodimer -- Flynn et al.
		Allosteric transition pathways in the lactose repressor protein core domains: Asymmetric motions in a homodimer
		Daly, T.J. and Matthews, K.S. Allosteric regulation of inducer and operator binding to the lactose repressor.
	www.proteinscience.org /cgi/content/full/12/11/2523 (7984 words)

	MOLECULAR BIOLOGY: ALLOSTERIC REGULATION OF RNA
		An important mechanism for controlling protein activity is allosteric regulation by a small molecule (i.e., binding of a small molecule to the protein at a location remote from the active site).
		Binding of this regulatory compound to the allosteric site induces structural rearrangements in the protein that are relayed to the active site, which then becomes either stable or unstable.
		In allosteric proteins, multiple subunits act cooperatively: Once a regulator is bound to one subunit, another subunit responds with dramatically enhanced affinity, allowing the protein's activity to be modulated as a function of slight changes in the regulator's concentration.
	scienceweek.com /2004/sc041119-1.htm (1615 words)

	E179: Xray Structural Studies Of Allosteric Effectors-Hemoglobin Complexes (Site not responding. Last check: 2007-09-06)
		Our goal is to understand the structural basis for the allosteric activity of a series of effectors of hemoglobin at the atomic level by means of X-ray crystallography.
		The substitution pattern at the anilino ring dictates the number of bound effector molecules, suggesting a possible explanation for differences in allosteric activity.
		The analysis of the refined structures reveals that changes in conformation of the bound effectors and of the water structure at the effector binding site might be also responsible for the differences in activity.
	www.hwi.buffalo.edu /ACA/ACA97/abstracts/text/E179.html (227 words)

	Answer Key for Re (Site not responding. Last check: 2007-09-06)
		In allosteric regulation, a metabolic pathway is controlled by an allosteric enzyme, which is normally an enzyme that catalyzes a reaction in the initial parts of a pathway.
		An allosteric enzyme has at least one allosteric site, which is a site apart from the active site, to which the allosteric regulator bonds reversibly.
		When the allosteric regulator is present in the allosteric site, the enzyme will either be in its active conformation or its inactive conformation, depending on whether the regulator is an inhibitor or an activator.
	www2.tltc.ttu.edu /dini/key2b(1403)00.htm (652 words)

	Rube Goldberg goes (ribo)nuclear? Molecular switches and sensors made from RNA -- SILVERMAN 9 (4): 377 -- RNA
		Allosteric (A) and inhibitor (B) control strategies for protein-mediated modulation of ribozyme activity, illustrated with the hammerhead ribozyme.
		In the classification proposed here, the inhibitor control strategies are not truly "allosteric" in that they do not involve a communication module.
		Jose, A.M., Soukup, G.A., and Breaker, R.R. Cooperative binding of effectors by an allosteric ribozyme.
	www.rnajournal.org /cgi/content/full/9/4/377 (3076 words)

	Separation of inhibition and activation of the allosteric yeast chorismate mutase -- Schnappauf et al. 95 (6): 2868 -- ...
		Separation of inhibition and activation of the allosteric yeast chorismate mutase -- Schnappauf et al.
		in the allosteric inhibition of yeast chorismate mutase.
		Tyr-234 in the allosteric inhibition of yeast chorismate mutase.
	www.pnas.org /cgi/content/full/95/6/2868 (3584 words)

	G Protein-Coupled Receptor Allosterism and Complexing -- Christopoulos and Kenakin 54 (2): 323 -- Pharmacological ...
		Allosteric ligand-mediated receptor-G protein interactions are not restricted to the muscarinic acetylcholine receptors.
		The quaternary complex model of allosteric interactions at GPCRs; a thermodynamically complete, extended model taking into account the concomitant binding of orthosteric ligand, A, allosteric ligand, B, and G protein, G, on a receptor that can exist in two conformational states (R and R).
		Allosteric interactions can be quite complex and there are a number of pharmacological approaches that are best used in tandem
	pharmrev.aspetjournals.org /cgi/content/full/54/2/323 (8902 words)

	allosteric control -- Encyclopædia Britannica
		More results on "allosteric control" when you join.
		The interaction changes the shape of the enzyme so as to affect the formation at the active site of the usual complex between the enzyme and its substrate (the compound upon which it...
		Allosteric control can operate in many ways; two examples serve to illustrate some general effects.
	www.britannica.com /eb/article-9005828?tocId=9005828 (847 words)

	Amnon Horovitz Homepage
		The focus of our research activities is to understand the molecular basis of allosteric transitions in proteins and how they relate to their function.
		According to this model, each ring of GroEL is in equilibrium between a T state (with low affinity for ATP and high affinity for protein substrates) and an R state (with high affinity for ATP and low affinity for protein substrates), in accordance with the concerted Monod-Wyman-Changeux model.
		We are currently analysing the allosteric mechanism of CCT, the eukaryotic homologue of GroEL.
	www.weizmann.ac.il /sb/faculty_pages/Horovitz/home.html (395 words)

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