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Your search keyword '"Newcomer, Marcia E."' showing total 264 results
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264 results on '"Newcomer, Marcia E."'

52. The structure and peroxidase activity of a 33-kDa catalase-related protein from Mycobacterium avium ssp. paratuberculosis

Author

Pakhomova, Svetlana, Gao, Benlian, Boeglin, William E, Brash, Alan R, and Newcomer, Marcia E

Subjects
Models, Molecular, Mycobacterium avium subsp. paratuberculosis, Protein Conformation, Molecular Sequence Data, Amino Acid Sequence, Heme, Catalase, Crystallography, X-Ray, Article, Peroxidase
Abstract

True catalases are tyrosine-liganded, usually tetrameric, hemoproteins with subunit sizes of approximately 55-84 kDa. Recently characterized hemoproteins with a catalase-related structure, yet lacking in catalatic activity, include the 40-43 kDa allene oxide synthases of marine invertebrates and cyanobacteria. Herein, we describe the 1.8 A X-ray crystal structure of a 33 kDa subunit hemoprotein from Mycobacterium avium ssp. paratuberculosis (annotated as MAP-2744c), that retains the core elements of the catalase fold and exhibits an organic peroxide-dependent peroxidase activity. MAP-2744c exhibits negligible catalatic activity, weak peroxidatic activity using hydrogen peroxide (20/s) and strong peroxidase activity (approximately 300/s) using organic hydroperoxides as co-substrate. Key amino acid differences significantly impact prosthetic group conformation and placement and confer a distinct activity to this prototypical member of a group of conserved bacterial "minicatalases". Its structural features and the result of the enzyme assays support a role for MAP-2744c and its close homologues in mitigating challenge by a variety of reactive oxygen species.

Published
2009

88. Detection of Conformational Changes in Cellular Retinoid-Binding Proteins by Limited Proteolysis.

Author

Walker, John M., Redfern, Christopher P. F., Jamison, Robert S., Newcomer, Marcia E., and Ong, David E.

Abstract

Partial proteolysis of an undenatured protein is a wtdely used, powerful technique to probe protein conformation in the native state. The basts for thts technique is that the more exposed an amino-acid residue is to the solvent, the easier it 1s for a protease to cleave a peptide bond at that site (1, 2). Therefore, regions of a protein with an extended conformation, such as those found in large multidomain proteins, are better substrates for proteolysis than are more tightly folded motifs. Using thus technique, it is possible to define protein domains, because the flexible regions between them are more susceptible to proteolysis. It is possible to further define these domains by obtaining N-terminal amino acid sequence of the resulting fragments. Likewise, by monitoring altered susceptibility to proteolysis, changes in protein conformation may be detected. If partial sequence of the resulting proteolytic fragments is obtained, the regions of the protein involved in these conformational changes can be mapped. [ABSTRACT FROM AUTHOR]

Published
1998
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89. Improving protein crystal quality by selective removal of a Ca2+-dependent membrane-insertion loop.

Author

Neau, David B., Gilbert, Nathaniel C., Bartlett, Sue G., Dassey, Adam, and Newcomer, Marcia E.

Subjects
PROTEINS, FATTY acids, LIPOXYGENASES, CRYSTALS, SPECTRUM analysis
Abstract

Lipoxygenases (LOXs) catalyze the regiospecific and stereospecific dioxygenation of polyunsaturated membrane-embedded fatty acids. A Ca2+-dependent membrane-binding function was localized to the amino-terminal C2-like domain of 8 R-lipoxygenase (8 R-LOX) from the soft coral Plexaura homomalla. The 3.2 Å crystal structure of 8 R-LOX and spectroscopic data suggested that Ca2+ stabilizes two membrane-insertion loops. Analysis of the protein packing contacts in the crystal lattice indicated that the conformation of one of the two loops complicated efforts to improve the resolution of the X-ray data. A deletion mutant of 8 R-LOX in which the corresponding membrane-insertion loop is absent (Δ41–45:GSLOX) was engineered. Removal of the membrane-insertion loop dramatically increases the protein yield from bacterial cultures and the quality of the crystals obtained, resulting in a better than 1 Å improvement in the resolution of the diffraction data. [ABSTRACT FROM AUTHOR]

Published
2007
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92. <atl>Protein folding and three-dimensional domain swapping: astrained relationship?

Author

Newcomer, Marcia E.

Subjects
*PROTEIN folding, *PROTEINS, *OLIGOMERS
Abstract

Many proteins function as multimeric assemblies into which the folded individual promoters organize as higher order structures. An oligomerization mechanism that appears to impose the coordination of events during folding and oligomer assembly is three-dimensional domain swapping. Recent studies have focused on revealing the structural basis of domain swapping and a possible role for domain swapping in the regulation of protein aggregation and activity. [Copyright &y& Elsevier]

Published
2002
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93. A helical lid converts a sulfotransferase to a dehydratase.

Author

Pakhomova, Svetlana, Kobayashi, Mime, Buck, Jochen, and Newcomer, Marcia E.

Subjects
TRANSFERASES, VITAMIN A, ENZYMES
Abstract

We report here the crystal structure of retinol dehydratase, an enzyme that catalyzes the synthesis of anhydroretinol. The enzyme is a member of the sulfotransferase superfamily and its crystal structure reveals the insertion of a helical lid into a canonical sulfotransferase fold. Site-directed mutations demonstrate that this inserted lid is necessary for anhydroretinol production but not for sulfonation; thus, insertion of a helical lid can convert a sulfotransferase into a dehydratase. [ABSTRACT FROM AUTHOR]

Published
2001
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94. Trading places.

Author

Newcomer, Marcia E.

Subjects
*AMYLOID beta-protein, *RIBONUCLEASES, *CYSTEINE proteinases
Abstract

Examines the role of domain swapping in the formation of amyloid fibrils. Information on the 3D domain swapping oligomerization mechanism; Significance of ribonuclease A structures; Description of the 3D domain swapped structure of cystatin C.

Published
2001
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95. Crystallization of retinol dehydratase from Spodoptera frugiperda: improvement of crystal quality by modification by ethylmercury- thiosalicylate.

Author

Pakhomova, Svetlana, Luz, John G., Kobayashi, Mime, Mellman, David, Buck, Jochen, and Newcomer, Marcia E.

Subjects
CRYSTALLIZATION, PHYSICAL & theoretical chemistry, SPODOPTERA, PROTEINS, CRYSTALS, DEHYDRATION
Abstract

Retinol dehydratase is a sulfotransferase which is presumed to catalyze the dehydration of its substrate via a transient retinyl sulfate intermediate. Crystals (space group P21, unit-cell parameters a = 82.05, b = 66.61, c = 84.90 Å, β = 111.29°) are significantly improved by covalent modification of the protein with ethylmercury. [ABSTRACT FROM AUTHOR]

Published
2000
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98. Crystal Structure of a Genomically Encoded Fosfomycin Resistance Protein (FosA) at 1.19 Å Resolution by MAD Phasing off L-III Edge of TI.

Author

Rife, Chris L., Pharris, Rachel E., Newcomer, Marcia E., and Armstrong, Richard N.

Subjects
*FOSFOMYCIN, *GLUTATHIONE, *CATALYSIS
Abstract

Examines the crystal structure of a genomically encoded fosfomycin resistance protein. Addition of glutathione to antibiotic fosfomycin; Roles of divalent and monovalent cations in catalysis; Intrinsic resistance of microbial genomes to antibiotics.

Published
2002
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99. Structure of a Calcium-dependent 11R-Lipoxygenase Suggests a Mechanism for Ca2+ Regulation.

Author

Eek, Priit, Järving, Reet, Järving, Ivar, Gilbert, Nathaniel C., Newcomer, Marcia E., and Samel, Nigulas

Subjects
*LIPOXYGENASES regulation, *INFLAMMATION, *ARACHIDONIC acid, *FATTY acids, *CALCIUM
Abstract

Lipoxygenases (LOXs) are a key part of several signaling pathways that lead to inflammation and cancer. Yet, the mechanisms of substrate binding and allosteric regulation by the various LOX isoforms remain speculative. Here we report the 2.47-Å resolution crystal structure of the arachidonate 11R-LOX from Gersemia fruticosa, which sheds new light on the mechanism of LOXcatalysis. Our crystallographic and mutational studies suggest that the aliphatic tail of the fatty acid is bound in a hydrophobic pocket with two potential entrances. We speculate that LOXs share a common T-shaped substrate channel architecture that gives rise to the varying positional specificities. A general allosteric mechanism is proposed for transmitting the activity inducing effect of calcium binding from the membrane-targeting PLAT (polycystin-1/lipoxygenase/α-toxin) domain to the active site via a conserved α-cation bridge. [ABSTRACT FROM AUTHOR]

Published
2012
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100. Expression of an 8R-Lipoxygenase From the Coral Plexaura homomalla.

Author

Gilbert NC, Neau DB, and Newcomer ME

Subjects
Animals, Arachidonate Lipoxygenases chemistry, Arachidonate Lipoxygenases genetics, Arachidonate Lipoxygenases metabolism, Arachidonic Acid chemistry, Binding Sites genetics, Crystallography, X-Ray methods, Escherichia coli metabolism, Metabolic Engineering methods, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins isolation & purification, Recombinant Proteins metabolism, Substrate Specificity genetics, Anthozoa metabolism, Arachidonate Lipoxygenases isolation & purification, Arachidonic Acid metabolism, Enzyme Assays methods, Protein Domains genetics
Abstract

Methods are presented for the use of the coral 8R-lipoxygenase from the Caribbean sea whip coral Plexaura homomalla as a model enzyme for structural studies of animal lipoxygenases. The 8R-lipoxygenase is remarkably stable and can be stored at 4°C for 3 months with virtually no loss of activity. In addition, an engineered "pseudo wild-type" enzyme is soluble in the absence of detergents, which helps facilitate the preparation of enzyme:substrate complexes., (© 2018 Elsevier Inc. All rights reserved.)

Published
2018
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