@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 {4447, title = {Pre-steady state kinetic analysis of an enzymatic reaction monitored by time-resolved electrospray ionization mass spectrometry}, journal = {Biochemistry}, volume = {37}, number = {21}, year = {1998}, note = {ISI Document Delivery No.: ZR717Times Cited: 73Cited Reference Count: 53}, month = {May}, pages = {7664-7669}, type = {Article}, abstract = {For the first time, the new technique of time-resolved electrospray ionization mass spectrometry (ESI-MS) has been used to accurately measure the pre-steady state kinetics of an enzymatic reaction by monitoring a transient enzyme intermediate. The enzyme used to illustrate this approach, Bacillus circulans xylanase, is a retaining glycosidase that hydrolyzes xylan or beta-xylobiosides through a double-displacement mechanism involving a covalent xylobiosyl-enzyme intermediate. A low steady state level of this intermediate formed during the hydrolysis of 2,5-dinitrophenyl beta-D-xylobioside was detected by time-resolved ESI-MS. The low concentration of this intermediate and its rate of formation did not permit pre-steady state kinetic analysis. By contrast, the covalent intermediate accumulates fully when the Tyr80Phe mutant hydrolyzes the same substrate. Using time-resolved ESI-MS, the pre-steady state kinetic parameters for the formation of the covalent intermediate in the mutant xylanase have been determined. The kinetic data are in agreement with those determined by monitoring the release of 2,5-dinitrophenol with stopped-flow W-vis spectroscopy. This demonstrates that time-resolved ESI-MS can be used to accurately monitor the pre-steady state kinetics of enzymatic reactions, with the advantage of identifying transient enzyme intermediates by their mass.}, keywords = {ACTIVE-SITE NUCLEOPHILE, AMINO-ACID, BACILLUS-CIRCULANS XYLANASE, beta-glucosidase, CELLULASES, CYTOCHROME-C, GAS-PHASE, IDENTIFICATION, inhibitors, MECHANISMS}, isbn = {0006-2960}, url = {://000074006700002}, author = {Zechel, D. L. and Konermann, L. and Withers, S. G. and Douglas, D. J.} } @article {3549, title = {PRODUCTION AND PROPERTIES OF A BIFUNCTIONAL FUSION PROTEIN THAT MEDIATES ATTACHMENT OF VERO CELLS TO CELLULOSIC MATRICES}, journal = {Biotechnology and Bioengineering}, volume = {47}, number = {2}, year = {1995}, note = {ISI Document Delivery No.: RD894Times Cited: 7Cited Reference Count: 29}, month = {Jul}, pages = {147-154}, type = {Article}, abstract = {The sequence Arg-Gly-Asp (RGD) in extracellular matrix proteins such as fibronectin, collagen, and laminin mediates cell attachment by interacting with proteins of the integrin family of cell surface receptors. A gene fusion encoding the RGD-containing peptide, fused to the C-terminus of a cellulose-binding domain (CBD/RGD), was expressed in Escherichia coli. Cultures produced up to 50 mg of CBD/RGD per titer, most of which was extracellular. it was purified from the culture supernatant by affinity chromatography on cellulose. CBD/RGD promoted the attachment of green monkey Vero cells to polystyrene and cellulose acetate. Attachment was inhibited by smalt synthetic peptides containing the RGD sequence. CBD/RGD was as effective as collagen in promoting the attachment of Vero cells to Cellsnow(TM) microcarriers. (C) 1995 John Wiley and Sons, Inc.}, keywords = {ADHESION, ARG-GLY-ASP, BINDING DOMAINS, BIOTECHNOLOGY, CELLULASES, CELLULOMONAS-FIMI, CELLULOSE, CULTURE, FIBRONECTIN, PROTEIN PRODUCTION, SEGMENT, SIGNAL, VITRONECTIN}, isbn = {0006-3592}, url = {://A1995RD89400004}, author = {Wierzba, A. and Reichl, U. and Turner, R. F. B. and Warren, R. A. J. and Kilburn, D. G.} }