@article {2546, title = {Ca2+ binding by domain 2 plays a critical role in the activation and stabilization of gelsolin}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, number = {33}, year = {2009}, note = {ISI Document Delivery No.: 484WETimes Cited: 5Cited Reference Count: 30Nag, Shalini Ma, Qing Wang, Hui Chumnarnsilpa, Sakesit Lee, Wei Lin Larsson, Marten Kannan, Balakrishnan Hernandez-Valladarez, Maria Burtnick, Leslie D. Robinson, Robert C.}, month = {Aug}, pages = {13713-13718}, type = {Article}, abstract = {Gelsolin consists of six homologous domains (G1-G6), each containing a conserved Ca-binding site. Occupation of a subset of these sites enables gelsolin to sever and cap actin filaments in a Ca-dependent manner. Here, we present the structures of Ca-free human gelsolin and of Ca-bound human G1-G3 in a complex with actin. These structures closely resemble those determined previously for equine gelsolin. However, the G2 Ca-binding site is occupied in the human G1-G3/actin structure, whereas it is vacant in the equine version. In-depth comparison of the Ca-free and Ca-activated, actin-bound human gelsolin structures suggests G2 and G6 to be cooperative in binding Ca2+ and responsible for opening the G2-G6 latch to expose the F-actin-binding site on G2. Mutational analysis of the G2 and G6 Ca-binding sites demonstrates their interdependence in maintaining the compact structure in the absence of calcium. Examination of Ca binding by G2 in human G1-G3/actin reveals that the Ca2+ locks the G2-G3 interface. Thermal denaturation studies of G2-G3 indicate that Ca binding stabilizes this fragment, driving it into the active conformation. The G2 Ca-binding site is mutated in gelsolin from familial amyloidosis (Finnish-type) patients. This disease initially proceeds through protease cleavage of G2, ultimately to produce a fragment that forms amyloid fibrils. The data presented here support a mechanism whereby the loss of Ca binding by G2 prolongs the lifetime of partially activated, intermediate conformations in which the protease cleavage site is exposed.}, keywords = {actin, AMYLOIDOGENESIS, biosynthesis, calcium, calcium activated, calcium dependent, FAMILIAL AMYLOIDOSIS, IDENTIFICATION, PLASMA GELSOLIN, PROTEIN, SITE, TERMINAL HALF, TIRF}, isbn = {0027-8424}, url = {://000269078700018}, author = {Nag, S. and Ma, Q. and Wang, H. and Chumnarnsilpa, S. and Lee, W. L. and Larsson, M. and Kannan, B. and Hernandez-Valladarez, M. and Burtnick, L. D. and Robinson, R. C.} } @article {2395, title = {The crystal structure of the C-terminus of adseverin reveals the actin-binding interface}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, number = {33}, year = {2009}, note = {ISI Document Delivery No.: 484WETimes Cited: 0Cited Reference Count: 21Chumnarnsilpa, Sakesit Lee, Wei Lin Nag, Shalini Kannan, Balakrishnan Larsson, Marten Burtnick, Leslie D. Robinson, Robert C.}, month = {Aug}, pages = {13719-13724}, type = {Article}, abstract = {Adseverin is a member of the calcium-regulated gelsolin superfamily of actin severing and capping proteins. Adseverin comprises 6 homologous domains (A1-A6), which share 60\% identity with the 6 domains from gelsolin (G1-G6). Adseverin is truncated in comparison to gelsolin, lacking the C-terminal extension that masks the F-actin binding site in calcium-free gelsolin. Biochemical assays have indicated differences in the interaction of the C-terminal halves of adseverin and gelsolin with actin. Gelsolin contacts actin through a major site on G4 and a minor site on G6, whereas adseverin uses a site on A5. Here, we present the X-ray structure of the activated C-terminal half of adseverin (A4-A6). This structure is highly similar to that of the activated form of the C-terminal half of gelsolin (G4-G6), both in arrangement of domains and in the 3 bound calcium ions. Comparative analysis of the actin-binding surfaces observed in the G4-G6/actin structure suggests that adseverin in this conformation will also be able to interact with actin through A4 and A6, whereas the A5 surface is obscured. A single residue mutation in A4-A6 located at the predicted A4/actin interface completely abrogates actin sequestration. A model of calcium-free adseverin, constructed from the structure of gelsolin, predicts that in the absence of a gelsolin-like C-terminal extension the interaction between A2 and A6 provides the steric inhibition to prevent interaction with F-actin. We propose that calcium binding to the N terminus of adseverin dominates the activation process to expose the F-actin binding site on A2.}, keywords = {74-KDA PROTEIN, ACTIVATION, calcium activated, EXOCYTOSIS, gelsolin, HALF, LOCALIZATION, SCINDERIN, SITE, TIRF}, isbn = {0027-8424}, url = {://000269078700019}, author = {Chumnarnsilpa, S. and Lee, W. L. and Nag, S. and Kannan, B. and Larsson, M. and Burtnick, L. D. and Robinson, R. C.} } @article {2277, title = {Phosphorylation of U24 from Human Herpes Virus type 6 (HHV-6) and its potential role in mimicking myelin basic protein (MBP) in multiple sclerosis}, journal = {Febs Letters}, volume = {582}, number = {18}, year = {2008}, note = {ISI Document Delivery No.: 332UKTimes Cited: 2Cited Reference Count: 31Tait, Andrew R. Straus, Suzana K.}, month = {Aug}, pages = {2685-2688}, type = {Article}, abstract = {Myelin basic protein (MBP) from multiple sclerosis ( MS) patients contains lower levels of phosphorylation at Thr97 than normal individuals. The significance of phosphorylation at this site is not fully understood, but it is proposed to play a role in the normal functioning of MBP. Human Herpesvirus Type 6 encodes the protein U24, which has tentatively been implicated in the pathology of MS. U24 shares a 7 amino acid stretch encompassing the Thr97 phosphorylation site of MBP: PRTPPPS. We demonstrate using a combination of mass spectrometry, thin layer chromatography and autoradiography, that U24 can be phosphorylated at the equivalent threonine. Phospho-U24 may confound signalling or other pathways in which phosphorylated MBP may participate, precipitating a pathological process.}, keywords = {BINDING, EXPRESSION, HUMAN-HERPESVIRUS-6, IDENTIFICATION, KINASE, MEMBRANE MICRODOMAINS, mimicry, myelin, PHOSPHORYLATION, POSTTRANSLATIONAL MODIFICATIONS, SITE, T-ANTIGEN, U24}, isbn = {0014-5793}, url = {://000258108400002}, author = {Tait, A. R. and Straus, S. K.} } @article {677, title = {The analysis of volatile trace compounds in landfill gases, compost heaps and forest air}, journal = {Applied Organometallic Chemistry}, volume = {17}, number = {3}, year = {2003}, note = {ISI Document Delivery No.: 651ZYTimes Cited: 7Cited Reference Count: 28}, month = {Mar}, pages = {154-160}, type = {Article}, abstract = {Landfill gas, cryotrapped on a loop fashioned from a length of a capillary gas chromatography (GC) column, was examined for volatile organometallic compounds (VOMCs) and for volatile organic compounds (VOCs) by using GC-mass spectrometry (MS). A large number of organic components were present and many were identified, but the only VOMCs present in high enough concentrations to be detected were trimethylstibine and tetramethyltin. The use of inductively coupled plasma (ICP)-MS as an element-specific detector allowed the identification of a number of other organometallic species in the landfill gas, including trimethylarsine and trimethylbismuth, and, for the first time, butyltrimethyltin and dibutyldimethyltin. The presence of molybdenum hexacarbonyl was confirmed. Gas from a large-scale compost heap and from compost incubated in the laboratory contained iodomethane but no common VOMCs (GC-ICP-MS). Only VOCs were present in forest air (GC-MS). Copyright (C) 2003 John Wiley Sons, Ltd.}, keywords = {(VOCs), BISMUTH, CHROMATOGRAPHY, EMISSIONS, ENVIRONMENT, GC-ICP-MS, GC-MS, METAL-COMPOUNDS, ORGANIC-COMPOUNDS, organotin speciation, phosphine, SITE, volatile organic compounds, volatile organometallic compounds (VONICs), WASTE}, isbn = {0268-2605}, url = {://000181355200002}, author = {Maillefer, S. and Lehr, C. R. and Cullen, W. R.} } @article {4578, title = {The cellulose-binding domains from Cellulomonas fimi beta-1,4-glucanase CenC bind nitroxide spin-labeled cellooligosaccharides in multiple orientations}, journal = {Journal of Molecular Biology}, volume = {287}, number = {3}, year = {1999}, note = {ISI Document Delivery No.: 184RGTimes Cited: 38Cited Reference Count: 46}, month = {Apr}, pages = {609-625}, type = {Article}, abstract = {The N-terminal cellulose-binding domains CBDN1 and CBDN2 from Cellulomonas fimi cellulase CenC each adopt a jelly-roll beta-sandwich structure with a cleft into which amorphous cellulose and soluble cellooligosaccharides bind. To determine the orientation of the sugar chain within these binding clefts, the association of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl-4-yl) spin-labeled derivatives of cellotriose and cellotetraose with isolated CBDN1 and CBDN2 was studied using heteronuclear H-1-N-15 NMR spectroscopy. Quantitative binding measurements indicate that the TEMPO moiety does not significantly perturb the affinity of the cellooligo-saccharide derivatives for the CBDs. The paramagnetic enhancements of the amide H-1(N) longitudinal (Delta R-1) and transverse (Delta R-2) relaxation rates were measured by comparing the effects of TEMPO-cellotetraose in its nitroxide (oxidized) and hydroxylamine (reduced) forms on the two CBDs. The bound spin-label affects most significantly the relaxation rates of amides located at both ends of the sugar-binding cleft of each CBD. Similar results are observed with TEMPO-cellotriose bound to CBDN1. This demonstrates that the TEMPO-labeled cellooligosaccharides, and by inference strands of amorphous cellulose, can associate with CBDN1 and CBDN2 in either orientation across their beta-sheet binding clefts. The ratio of the association constants for binding in each of these two orientations is estimated to be within a factor of five to tenfold. This finding is consistent with the approximate symmetry of the hydrogen-bonding groups on both the cellooligosaccharides and the residues forming the binding clefts of the CenC CBDs. (C) 1999 Academic Press.}, keywords = {CELLULASES, ENDOGLUCANASE, GLYCOSYNTHASE, MAGNETIC-RESONANCE SPECTROSCOPY, NMR, protein-carbohydrate interaction, PROTEINS, SENSITIVITY, SITE, SPECIFICITY, spin label}, isbn = {0022-2836}, url = {://000079626300013}, author = {Johnson, P. E. and Brun, E. and Mackenzie, L. F. and Withers, S. G. and McIntosh, L. P.} } @article {4298, title = {Epimerization via carbon-carbon bond cleavage. L-ribulose-5-phosphate 4-epimerase as a masked class II aldolase}, journal = {Biochemistry}, volume = {37}, number = {16}, year = {1998}, note = {ISI Document Delivery No.: ZM208Times Cited: 32Cited Reference Count: 35}, month = {Apr}, pages = {5746-5754}, type = {Article}, abstract = {Studies indicating that the E. coli L-ribulose-5-phosphate 4-epimerase employs an "aldolase-like" mechanism are reported. This NAD(+)-independent enzyme epimerizes a steseocenter that does not bear an acidic proton and therefore it cannot utilize a simple deprotonation-reprotonation mechanism. Sequence similarities between the epimerase and the class II L-fuculose-1-phosphate aldolase suggest that the two may be evolutionarily related and that the epimerization may occur via carbon-carbon bond cleavage and re-formation. Conserved residues thought to provide the metal ion ligands of the epimerase have been modified using site-directed mutagenesis. The resulting mutants show low k(cat) values in addition to a reduced affinity for Zn2+. These observations serve to establish that there is a structural link between between the active site geometry of the epimerase and the aldolase. In addition, the H97N mutant was found to catalyze the condensation of dihydroxyacetone and glycolaldehyde phosphate to produce a mixture of L-ribulose-5-phosphate and D-xylulose-5-phosphate. This observation of aldolase activity establishes that the epimerase active site is capable of promoting carbon-carbon bond cleavage. Furthermore, glycolaldehyde phosphate was shown to be a competitive inhibitor of the mutant enzyme (K-t = 0.37 mM) but not of the wild-type enzyme. The mutation apparently causes the epimerase to become "leaky" and enables it to bind/generate the normal reaction intermediates from the unbound aldol cleavage products.}, keywords = {ENZYMES, ESCHERICHIA-COLI, L-FUCULOSE-1-PHOSPHATE ALDOLASE, MECHANISM, MUTAGENESIS, ORGANIC-SYNTHESIS, PCR, PURIFICATION, SEQUENCE, SITE}, isbn = {0006-2960}, url = {://000073515500048}, author = {Johnson, A. E. and Tanner, M. E.} } @article {3186, title = {TENSOR LEED ANALYSIS OF THE CU(110)-(2 X 3)-N SURFACE-STRUCTURE}, journal = {Physical Review B}, volume = {49}, number = {16}, year = {1994}, note = {ISI Document Delivery No.: NK063Times Cited: 27Cited Reference Count: 25}, month = {Apr}, pages = {11515-11518}, type = {Note}, abstract = {A tensor LEED analysis of the Cu(110)-(2 x 3)-N surface structure supports. a reconstruction model in which the topmost layer can be described as a pseudo-(100)-c(2 x 2)-N overlayer, with metal corrugation of about 0.52 angstrom in the reconstructed layer. Each N atom is nearly coplanar with the local plane formed by the four neighboring Cu atoms. Of the four N atoms per unit mesh, three also bond to Cu atoms in the layer below and are therefore five-coordinate. Two of the three five-coordinate sites result from appreciable lateral displacements toward each other of both N atoms and Cu atoms below in the topmost Cu(110) layer. Average N-Cu bond lengths for the five-coordinate sites (1.87 angstrom) agree well with prediction, while the bond lengths for the four-coordinate sites (1.85 angstrom) appear somewhat long. These different N sites are discussed in relation to a recent STM study, and results from this LEED analysis are contrasted with those from the previous LEED study, which supported a [001]-missing row reconstruction of the surface.}, keywords = {CU(110)(2X3)-N STRUCTURE, ENERGY-ELECTRON-DIFFRACTION, ION-SCATTERING, NITRIDE, NITROGEN, RECONSTRUCTION, SITE, SUBSTRATE}, isbn = {0163-1829}, url = {://A1994NK06300093}, author = {Vu, D. T. and Mitchell, K. A. R.} } @article {7321, title = {BINDING-ENERGY AND CATALYSIS - FLUORINATED AND DEOXYGENATED GLYCOSIDES AS MECHANISTIC PROBES OF ESCHERICHIA-COLI (LACZ) BETA-GALACTOSIDASE}, journal = {Biochemical Journal}, volume = {286}, year = {1992}, note = {ISI Document Delivery No.: JN815Times Cited: 86Cited Reference Count: 40Part 3}, month = {Sep}, pages = {721-727}, type = {Article}, abstract = {Kinetic parameters for the hydrolysis of a series of deoxy and deoxyfluoro analogues of 2{\textquoteright},4{\textquoteright}-dinitrophenyl beta-D-galactopyranoside by Escherichia coli (lacZ) beta-galactosidase have been determined and rates found to be two to nine orders of magnitude lower than that for the parent compound. These large rate reductions result primarily from the loss of transition-state binding interactions due to the replacement of sugar hydroxy groups, and such interactions are estimated to contribute at least 16.7 kJ (4 kcal).mol-1 to binding at the 3, 4 and 6 positions and more than 33.5 kJ (8 kcal).mol-1 at the 2 position. The existence of a linear free-energy relationship between log(k(cat.)/K(m)) for these compounds and the logarithm of the first-order rate constant for their spontaneous hydrolysis demonstrates that electronic effects are also important and provides direct evidence for oxocarbonium ion character in the enzymic transition state. A covalent intermediate which turns over only extremely slowly (t1/2 = 45 h) accumulates during hydrolysis of the 2-deoxyfluorogalactoside, and kinetic parameters for its formation have been determined. This intermediate is nonetheless catalytically competent, since it re-activates much more rapidly in the presence of the transglycosylation acceptors methanol or glucose, thereby providing support for the notion of a covalent intermediate during hydrolysis of the parent substrates.}, keywords = {ALPHA-D-GLUCOPYRANOSYL, D-GLUCOPYRANOSYL PHOSPHATES, ENZYME, GLYCOGEN-PHOSPHORYLASE, HYDROLYSIS, inhibitors, OLIGOSACCHARIDE, SITE, SPECIFICITY, SUBSTRATE}, isbn = {0264-6021}, url = {://A1992JN81500010}, author = {McCarter, J. D. and Adam,Michael J. and Withers, S. G.} } @article {7249, title = {LEED CRYSTALLOGRAPHIC STUDIES FOR THE CU(110)-(2 X 3)-N SURFACE-STRUCTURE}, journal = {Surface Science}, volume = {271}, number = {3}, year = {1992}, note = {ISI Document Delivery No.: JA639Times Cited: 19Cited Reference Count: 31}, month = {Jun}, pages = {519-529}, type = {Article}, abstract = {An initial multiple-scattering analysis of LEED intensities has been performed for the Cu(110)-(2 x 3)-N surface structure. R-factor analysis supports neither simple N overlayer models nor models with Cu(100)-type top-layer reconstructions. The best correspondence between calculated and experimental intensities appears with models where every other [001] row is missing, similar to that observed for the Cu(110)-(2 x 1)-O surface. The favoured surface structure has N atoms chemisorbed on long-bridge sites such that chains of (Cu(a)-N-Cu(b)-N-Cu(a))x create a surface analogous to the ideal Cu3N(110) surface, except that every third N atom is missing from the surface chains. There is evidence that lateral displacement of copper atoms from the ideal positions leads to two different N-Cu surface bond lengths with values near 1.83 and 1.90 angstrom. Each N atom also bonds to two Cu atoms in the second layer with equal bond lengths of about 1.88 angstrom.}, keywords = {ADSORPTION, AES, chemisorption, CU(110)(2X3)-N STRUCTURE, ENERGY ELECTRON-DIFFRACTION, NI(110), NITRIDE, NITROGEN, RECONSTRUCTION, SITE}, isbn = {0039-6028}, url = {://A1992JA63900025}, author = {Grimsby, D. T. V. and Zhou, M. Y. and Mitchell, K. A. R.} }