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Background: Cellulases, which catalyze the hydrolysis of glycosidic bonds in cellulose, can be classified into several different protein families. Endoglucanase CelA is a member of glycosyl hydrolase family 8, a family for which no structural information was previously available.Results The crystal structure of CelA was determined by multiple isomorphous replacement and refined to 1.65 a resolution...
Background: Transaldolase is one of the enzymes in the non-oxidative branch of the pentose phosphate pathway. It transfers a C3 ketol fragment from a ketose donor to an aldose acceptor. Transaldolase, together with transketolase, creates a reversible link between the pentose phosphate pathway and glycolysis. The enzyme is of considerable interest as a catalyst in stereospecific organic synthesis and...
Background The enzyme 1,3,8-trihydroxynaphthalene reductase (THNR) catalyzes an essential reaction in the biosynthesis of melanin, a black pigment crucial for the pathogenesis of the rice blast fungus, Magnaporthe grisea. The enzyme is the biochemical target of several commercially important fungicides which are used to prevent blast disease in rice plants. We have determined the structure of the...
Background G proteins play a vital role in transmembrane signalling events. In their inactive form G proteins exist as heterotrimers consisting of an α subunit, complexed with GDP and a dimer of βγ subunits. Upon stimulation by receptors, G protein α subunits exchange GDP for GTP and dissociate from βγ . Thus activated, αsubunits stimulate or inhibit downstream effectors. The duration of the activated...
Background: Copper-containing amine oxidases (CAOs) are widespread in nature. These enzymes oxidize primary amine substrates to the aldehyde product, reducing molecular oxygen to hydrogen peroxide in the process. CAOs contain one type 2 copper atom and topaquinone (TPQ), a modified tyrosine sidechain utilized as a redox cofactor. The methylamine oxidase from the yeast Hansenula polymorpha (HPAO) is...
Background: The synthesis of phenolic compounds as by-products of industrial reactions poses a serious threat to the environment. Understanding the enzymatic reactions involved in the degradation and detoxification of these compounds is therefore of much interest. Soil-living yeasts use flavin adenine dinucleotide (FAD)-containing enzymes to hydroxylate phenols. This reaction initiates a metabolic...
Background: Monomeric sarcosine oxidases (MSOXs) are among the simplest members of a recently recognized family of eukaryotic and prokaryotic enzymes that catalyze similar oxidative reactions with various secondary or tertiary amino acids and contain covalently bound flavins. Other members of this family include heterotetrameric sarcosine oxidase, N-methyltryptophan oxidase and pipecolate oxidase...
Background: Pyruvate formate lyase (PFL) catalyses a key step inEscherichia coli anaerobic glycolysis by converting pyruvate and CoA to formate and acetylCoA. The PFL mechanism involves an unusual radical cleavage of pyruvate, involving an essential Cα radical of Gly734 and two cysteine residues, Cys418 and Cys419, which may form thiyl radicals required for catalysis. We undertook this study to understand...
Background: DNA topoisomerases are enzymes that change the topology of DNA. Type IA topoisomerases transiently cleave one DNA strand in order to pass another strand or strands through the break. In this manner, they can relax negatively supercoiled DNA and catenate and decatenate DNA molecules. Structural information on Escherichia coli DNA topoisomerase III is important for understanding the mechanism...
Background: The bacterial cell wall and the enzymes that synthesize it are targets of glycopeptide antibiotics (vancomycins and teicoplanins) and β-lactams (penicillins and cephalosporins). Biosynthesis of cell wall peptidoglycan requires a crosslinking of peptidyl moieties on adjacent glycan strands. The d-alanine-d-alanine transpeptidase, which catalyzes this crosslinking, is the target of β-lactam...
Background: Phytases hydrolyze phytic acid (myo-inositol-hexakisphosphate) to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are used in animal feed to reduce phosphate pollution in the environment. Recently, a thermostable, calcium-dependent Bacillus phytase was identified that represents the first example of the β propeller fold exhibiting phosphatase activity. We...
Background: 5'-methylthioadenosine/S-adenosyl-homocysteine (MTA/AdoHcy) nucleosidase catalyzes the irreversible cleavage of 5'-methylthioadenosine and S-adenosylhomocysteine to adenine and the corresponding thioribose, 5'-methylthioribose and S-ribosylhomocysteine, respectively. While this enzyme is crucial for the metabolism of AdoHcy and MTA nucleosides in many prokaryotic and lower eukaryotic organisms,...
The structure of the type II DHQase from Streptomyces coelicolor has been solved and refined to high resolution in complexes with a number of ligands, including dehydroshikimate and a rationally designed transition state analogue, 2,3-anhydro-quinic acid. These structures define the active site of the enzyme and the role of key amino acid residues and provide snap shots of the catalytic cycle. The...
Glycosyltransferases (GTs) play a central role in nature. They catalyze the transfer of a sugar moiety to a broad range of acceptor substrates. GTs are highly selective enzymes, allowing the recognition of subtle structural differences in the sequences and stereochemistry of their sugar and acceptor substrates. We report here a series of structural snapshots of the reaction center of the retaining...
The endoplasmic reticulum (ER) forms a branched, dynamic membrane tubule network that is vital for cellular function. Branching arises from membrane fusion facilitated by the GTPase atlastin (ATL). Many metazoan genomes encode for three ATL isoforms that appear to fulfill partially redundant function despite differences in their intrinsic GTPase activity and localization within the ER; however, the...
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