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Background: Cytochromes P450 catalyze the oxidation of a variety of hydrophobic substrates. Sequence identities between P450 families are generally low (10-30%), and consequently, the structure-function correlations among P450s are not clear. The crystal structures of P450 terp and the hemoprotein domain of P450 BM-3 were recently determined, and are compared...
Background: The coat protein in RNA bacteriophages binds and encapsidates viral RNA, and also acts as translational repressor of viral replicase by binding to an RNA hairpin in the RNA genome. Because of its dual function, the MS2 coat protein is an interesting candidate for structural studies of protein-RNA interactions and protein-protein interactions. In this study, unassembled MS2 coat protein...
Background: Tetrahydrobiopterin serves as the cofactor for enzymes involved in neurotransmitter biosynthesis and as a regulatory factor in immune cell proliferation and the biosynthesis of melanin. The biosynthetic pathway to tetrahydrobiopterin consists of three steps starting from GTP. The initial reaction is catalyzed by GTP cyclohydrolase I (GTP-CH-I) and involves the chemically complex transformation...
Background: Haemopexin is a serum glycoprotein that binds haem reversibly and delivers it to the liver where it is taken up by receptor-mediated endocytosis. Haemopexin has two homologous domains, each having a characteristic fourfold internal sequence repeat. Haemopexin-type domains are also found in other proteins, including the serum adhesion protein vitronectin and various collagenases, in which...
Background: HIV reverse transcriptase (RT) is a key target of anti-AIDS therapies. Structural studies of HIV-1 RT, unliganded and complexed with different non-nucleoside inhibitors (NNIs), have pointed to a common mode of binding and inactivation through distortion of the polymerase catalytic site by NNIs containing two hinged rings. The mode of binding of the TIBO family of inhibitors is of interest...
Background: OmpF porin is a trimeric integral membrane protein responsible for the passive transport of small hydrophilic molecules, such as nutrients and waste products, across the outer membrane of Escherichia coli. Very few membrane proteins have been crystallized in three dimensions, yet this stable protein can be obtained in several crystal forms. Comparison of the structures of the same membrane...
Background: Electron transfer between cytochrome f and photosystem I (PSI) can be accomplished by the heme-containing protein cytochrome c 6 or by the copper-containing protein plastocyanin. Higher plants use plastocyanin as the only electron donor to PSI, whereas most green algae and cyanobacteria can use either, with similar kinetics, depending on the copper concentration in the culture...
Background: Infections caused by Candida albicans, a common fungal pathogen of humans, are increasing in incidence, necessitating development of new therapeutic drugs. Secreted aspartic proteinase (SAP) activity is considered an important virulence factor in these infections and might offer a suitable target for drug design. Amongst the various SAP isozymes, the SAP2 gene product is the major form...
Background: Integrins are plasma membrane proteins that mediate adhesion to other cells and to components of the extracellular matrix. Most integrins are constitutively inactive in resting cells, but are rapidly and reversibly activated in response to agonists, leading to highly regulated cell adhesion. This activation is associated with conformational changes in their extracellular portions, but...
Background: Escherichia coli β-hydroxydecanoyl thiol ester dehydrase (dehydrase) is essential to the biosynthesis of unsaturated fatty acids, by shunting a 10-carbon intermediate from the saturated fatty acid pathway into the unsaturated fatty acid pathway. Dehydrase catalyzes reactions of dehydration and of double-bond isomerization on 10-carbon thiol esters of acyl carrier protein (ACP). The aim...
Background: Peroxidases catalyze a wide variety of peroxide-dependent oxidations. Based on sequence alignments, heme peroxidases have been divided into three classes. Crystal structures are available for peroxidases of classes I and II, but until now no structure has been determined for class III, the classical extracellular plant peroxidases.Results The crystal structure of peanut peroxidase has...
Background: The ubiquitous pyruvate dehydrogenase multienzyme complex is built around an octahedral or icosahedral core of dihydrolipoamide acetyltransferase (E2) chains, to which multiple copies of pyruvate decarboxylase (E1) and dihydrolipoamide dehydrogenase (E3) bind tightly but non-covalently. E2 is a flexible multidomain protein that mediates interactions with E1 and E3 through a remarkably...
Background: α-Conotoxins are peptide toxins, isolated from Conus snails, that block the nicotinic acetylcholine receptor (nAChR). The 16-residue peptides PnIA and PnIB from Conus pennaceus incorporate the same disulfide framework as other α-conotoxins but differ in function from most α-conotoxins by blocking the neuronal nAChR, rather than the skeletal muscle subtype. The crystal structure determination...
Background: Glycogen phosphorylases consist of a conserved catalytic core onto which different regulatory sites are added. By comparing the structures of isozymes, we hope to understand the structural principles of allosteric regulation in this family of enzymes. Here, we focus on the differences in the glucose 6-phosphate (Glc-6-P) binding sites of two isozymes.Results We have refined the structure...
Background: The capsid protein subunits of small RNA bacteriophages form a T=3 particle upon assembly and RNA encapsidation. Dimers of the capsid protein repress translation of the replicase gene product by binding to the ribosome binding site and this interaction is believed to initiate RNA encapsidation. We have determined the crystal structure of phage Qβ with the aim of clarifying which factors...
Background: Spo0F, a phosphotransferase containing an aspartyl pocket, is involved in the signaling pathway (phosphorelay) controlling sporulation in Bacillus subtilis. It belongs to the superfamily of bacterial response regulatory proteins, which are activated upon phosphorylation of an invariant aspartate residue. This phosphorylation is carried out in a divalent cation dependent reaction catalyzed...
Background: Amidotransferases use the amide nitrogen of glutamine in a number of important biosynthetic reactions. They are composed of a glutaminase domain, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, and a synthetase domain, catalyzing amination of the substrate. To gain insight into the mechanism of nitrogen transfer, we examined the structure of the glutaminase domain...
Background Copper-containing amine oxidases catalyze the oxidative deamination of primary amines to aldehydes, in a reaction that requires free radicals. These enzymes are important in many biological processes, including cell differentiation and growth, would healing, detoxification and signalling. The catalytic reaction requires a redox cofactor, topa quinone (TPQ), which is derived by post-translational...
Background The essential enzyme dUTP pyrophosphatase (dUTPase) is exquisitely specific for dUTP and is critical for the fidelity of DNA replication and repair. dUTPase hydrolyzes dUTP to dUMP and pyrophosphate, simultaneously reducing dUTP levels and providing the dUMP for dTTP biosynthesis. A high cellular dTTP: dUTP ratio is essential to avoid uracil incorporation into DNA, which would lead to strand...
Background Aldolases catalyze a variety of condensation and cleavage reactions, with exquisite control on the stereochemistry. These enzymes, therefore, are attractive catalysts for synthetic chemistry. There are two classes of aldolase: class I aldolases utilize Schiff base formation with an active-site lysine whilst class II enzymes require a divalent metal ion, in particular zinc. Fructose-1,6-bisphosphate...
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