@article {2279,
	title = {Transient oxidation as a mechanistic strategy in enzymatic catalysis},
	journal = {Current Opinion in Chemical Biology},
	volume = {12},
	number = {5},
	year = {2008},
	note = {ISI Document Delivery No.: 375SZTimes Cited: 1Cited Reference Count: 41Tanner, Martin E.},
	month = {Oct},
	pages = {532-538},
	type = {Review},
	abstract = {Enzymes that employ a transient oxidation mechanism catalyze transformations that are overall redox neutral, but involve intermediates that have a higher oxidation state than the substrates or products. An oxidation/reduction sequence may be used directly to promote isomerization reactions or indirectly to permit the formation of stabilized intermediates such as carbanions. This review will focus on three recent examples of nicotinamide-dependent enzymes that have been found to employ transient oxidation during catalysis: ADP-L-glycero-D-manno-heptose 6-epimerase, GDP-mannose 3,5-epimerase, and the 6-phosphoglucosidases from family 4. These enzymes are remarkable in their ability to catalyze either nonstereospecific hydride transfers or multiple chemical steps within a single active site.},
	keywords = {ACTIVE-SITE, ALPHA-GLUCOSIDASE, BACILLUS-SUBTILIS, CRYSTAL-STRUCTURE, D-MANNO-HEPTOSE, D-MANNOHEPTOSE 6-EPIMERASE, DEHYDROQUINATE SYNTHASE, ESCHERICHIA-COLI, THERMOTOGA-MARITIMA, UDP-GALACTOSE 4-EPIMERASE},
	isbn = {1367-5931},
	url = {<Go to ISI>://000261134900010},
	author = {Tanner, M. E.}
}
@article {976,
	title = {Structural characterization of the RNase E S1 domain and identification of its oligonucleotide-binding and dimerization interfaces},
	journal = {Journal of Molecular Biology},
	volume = {341},
	number = {1},
	year = {2004},
	note = {ISI Document Delivery No.: 841JCTimes Cited: 25Cited Reference Count: 65},
	month = {Jul},
	pages = {37-54},
	type = {Article},
	abstract = {S1 domains occur in four of the major enzymes of mRNA decay in Escherichia coli: RNase E, PNPase, RNase II, and RNase G. Here, we report the structure of the S1 domain of RNase E, determined by both X-ray crystallography and NMR spectroscopy. The RNase E S1 domain adopts an OB-fold, very similar to that found with PNPase and the major cold shock proteins, in which flexible loops are appended to a well-ordered five-stranded beta-barrel core. Within the crystal lattice, the protein forms a dimer stabilized primarily by intermolecular hydrophobic packing. Consistent with this observation, light-scattering, chemical crosslinking, and NMR spectroscopic measurements confirm that the isolated RNase E S1 domain undergoes a specific monomer-dimer equilibrium in solution with a K-D value in the millimolar range. The substitution of glycine 66 with serine dramatically destabilizes the folded structure of this domain, thereby providing an explanation for the temperature-sensitive phenotype associated with this mutation in full-length RNase E. Based on amide chemical shift perturbation mapping, the binding surface for a single-stranded DNA dodecamer (K-D = 160(+/-40) muM) was identified as a groove of positive electrostatic potential containing several exposed aromatic side-chains. This surface, which corresponds to the conserved ligand-binding cleft found in numerous OB-fold proteins, lies distal to the dimerization interface, such that two independent oligonucleotide-binding sites can exist in the dimeric form of the RNase E S1 domain. Based on these data, we propose that the S1 domain serves a dual role of dimerization to aid in the formation of the tetrameric quaternary structure of RNase E as described by Callaghan et al. in 2003 and of substrate binding to facilitate RNA hydrolysis by the adjacent catalytic domains within this multimeric enzyme. (C) 2004 Elsevier Ltd. All rights reserved.},
	keywords = {BACILLUS-SUBTILIS, C-13-LABELED PROTEINS, CELLULOMONAS-FIMI, CENC, CHEMICAL-SHIFT, COLD-SHOCK PROTEIN, ESCHERICHIA-COLI, MACROMOLECULAR STRUCTURES, MESSENGER-RNA, OB-fold, protein structure, RNA binding, RNase E, ROTATIONAL DIFFUSION, S1 domain, SELECTIVE H-1-N-15 CORRELATIONS},
	isbn = {0022-2836},
	url = {<Go to ISI>://000222925100005},
	author = {Schubert, M. and Edge, R. E. and Lario, P. and Cook, M. A. and Strynadka, N. C. J. and Mackie, G. A. and McIntosh, L. P.}
}
@article {4074,
	title = {Eliminations in the reactions catalyzed by UDP-N-acetylglucosamine 2-epimerase},
	journal = {Journal of the American Chemical Society},
	volume = {119},
	number = {43},
	year = {1997},
	note = {ISI Document Delivery No.: YD815Times Cited: 33Cited Reference Count: 65},
	month = {Oct},
	pages = {10269-10277},
	type = {Article},
	abstract = {Mechanistic studies have been carried out on the bacterial enzyme UDP-N-acetylglucosamine 2-epimerase, which catalyzes the interconversion of UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylmannosamine (UDP-ManNAc). This enzyme is interesting because it epimerizes a stereocenter that does not bear an acidic proton, and therefore it cannot utilize a simple deprotonation/reprotonation mechanism. A coupled enzyme assay employing UDP-ManNAc dehydrogenase has been developed. The epimerization in D2O is found to be accompanied by the incorporation of deuterium into the C-2 {\textquoteright}{\textquoteright} position of both epimers, supporting a mechanism that ultimately involves a proton transfer at this position. The epimerization of [2 {\textquoteright}{\textquoteright}-H-2]UDP-GlcNAc is slowed by a primary kinetic isotope effect indicating that C-H bond cleavage is occurring during a rate-determining step of the reaction. A positional isotope exchange (PM) experiment shows that an O-18 label in the sugar-UDP bridging position will scramble into nonbridging diphosphate positions during enzymatic epimerization. These observations are consistent with a mechanism that proceeds via cleavage of the anomeric C-O bond, with 2-acetamidoglucal and UDP as enzyme-bound intermediates. Additional evidence for this mechanism is found in the unusual observation that during extended incubations, the intermediates are gradually released from the enzyme and accumulate in solution. These intermediates are formed by an anti elimination of UDP from UDP-GlcNAc and a syn elimination of UDP from UDP-ManNAc. It is likely that El-like eliminations via oxocarbenium intermediates are involved in the reaction. Further experiments show that 3 {\textquoteright}{\textquoteright}-deoxy-UDP-GlcNAc is not a substrate for the enzyme and that the enzyme does not contain a tightly bound NAD(+) cofactor.},
	keywords = {BACILLUS-SUBTILIS, D-GLUCOSAMINE 2-EPIMERASE, enterobacterial common antigen, ESCHERICHIA-COLI, FATTY-ACID OXIDATION, GALACTOSE 4-EPIMERASE, POSITIONAL ISOTOPE EXCHANGE, RAT-LIVER, STAPHYLOCOCCUS-AUREUS-H, TEICHOIC-ACIDS, W23},
	isbn = {0002-7863},
	url = {<Go to ISI>://A1997YD81500003},
	author = {Morgan, P. M. and Sala, R. F. and Tanner, M. E.}
}
