ISSN:1399-0047    

DOI:10.1107/S0907444995099756

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

X‐ray diffraction data collected at cryogenic temperatures from flash‐cooled crystals of influenza virus hemagglutinin show improvements in both resolution and quality relative to data collected at 277 K. These improvements are dramatic for flash‐cooled hemagglutinin crystals irradiated with X‐rays from a synchrotron source. At the Cornell High Energy Synchrotron Source flash‐cooled hemagglutinin crystals diffracted at least 0.9 Å farther than hemagglutinin crystals at ambient temperatures. Radiation damage in the flash‐cooled crystals is reduced, making it possible to collect a complete data set from a single hemagglutinin crystal. However, radiation damage is not eliminated in the flash‐cooled crystal. As a result the quality of X‐ray data can be significantly degraded during long exposure times at

ISSN:1399-0047    

DOI:10.1107/S090744499400822X

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

A general method to deconvolute oscillation data sets from twinned protein crystals to a corresponding single‐crystal data set has been developed and applied to diffraction data measured from crystals of a fragment containing the FAD‐ and NADH‐binding domains of nitrate reductase. The procedure allows straightforward processing of diffraction data from twinned crystals. Typically,Rmergevalues of reduced data sets from the nitrate reductase crystals after deconvolution are about 0.06 compared to 0.13 and higher before deconvolution. Based on these deconvoluted data sets, the structure of the FAD‐ and NADH‐binding domains of nitrate reductase could be solved successfully. The result indicates that crystal twinning does not necessarily prevent crystallographic structure dete

ISSN:1399-0047    

DOI:10.1107/S0907444994008693

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

The crystal structure of heme domain of the fatty acid monooxygenase, cytochrome P450BM‐3, consisting of residues 1–455 has been independently solved toR= 0.18 at 2.0 Å. The crystal form used, space groupP21with two molecules per asymmetric unit, is isomorphous with that form with residues 1–471 first described by Boddupalliet al.[Boddupalli, Hasemann, Ravinchandran, Lu, Goldsmith, Deisenhofer&Peterson (1992).Proc. Natl Acad. Sci. USA,89, 5567–5571] and used by Ravichandran, Boddupalli, Hasemann, Peterson&Deisenhofer [(1993).Science,261, 731–736] to determine the crystal structure. The substrate‐access channel consists of a large, hydrophobic cleft that appears to be the most likely route taken by fatty acid substrates. Attempts to soak crystals in mother liquor containing a variety of fatty acid substrates yielded featureless difference Fouriers even though fatty acid substrates are known to bind with dissociation constants in the µMrange. Modeling substrate–enzyme interactions reveals few contacts between the enzyme and substrate. More detailed modeling was carried out by subjecting both molecules in the asymmetric unit to extensive energy minimization. These studies reveal that the heme‐domain active‐site cleft can undergo a large conformational change that closes the access channel thereby providing enhanced protein–substrate interactions. These conformational changes are prevented from occurring by intermolecular contacts in the crystal lattice which lock the protein in

ISSN:1399-0047    

DOI:10.1107/S0907444994009194

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

The crystal structure of crambin, a 46‐residue protein containing the equivalent of approximately 400 fully occupied non‐H‐atom positions, was originally solved at 1.5 Å by exploiting the anomalous scattering of its six S atoms at a single wavelength far removed from the absorption edge of sulfur. The crambin structure has now been resolved without the use of any anomalous‐dispersion measurements. The technique employed was anab initio`shake‐and‐bake' method, consisting of a phase‐refinement procedure based on the minimal function alternated with Fourier refinement. This method has successfully yielded solutions for a smaller molecule (28 atoms) using 1.2 Å data, and a crambin solution wa

ISSN:1399-0047    

DOI:10.1107/S090744499400925X

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

OppA is a 58.8 kDa bacterial transport protein involved in the transport of peptides across the cytoplasmic membrane of Gram‐negative bacteria. It binds peptides from two to five residues in length but with little sequence specificity. OppA fromSalmonella typhimuriumhas been cloned and expressed inE. coliand the protein cocrystallized with uranyl acetate, producing two distinct crystal forms with different uranium sites. Multiple‐wavelength data collected about the uraniumLIIIedge have been collected at the Daresbury Synchrotron Radiation Source (SRS) to a nominal resolution limit of 2.3 Å. Maximum‐likelihood phasing methods have been used in phase determination from the multiple‐wavelength data giving a readily interpretable electron‐density map, without any density modification. The electron‐density map, calculated at 2.3 Å resolution shows OppA to be a bilobal, principally β‐stranded, three‐domain protein. The tri‐lysine ligand molecule can be clearly seen in the peptide‐bindin

ISSN:1399-0047    

DOI:10.1107/S090744499400692X

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

Octreotide, a synthetic somatostatin analogue, is an octapeptide with one disulfide bridge. Crystals of octreotide are orthorhombic, space groupP212121,a= 18.458 (5),b= 30.009 (7),c= 39.705 (27) Å, with three molecules of octapeptide, one ordered oxalate dianion and 52 water molecules in the asymmetric unit. Complete protonation of the NH2groups (as assumed in the refinement) would require three oxalate dianions in the asymmetric unit for charge neutrality; a chemical analysis indicated that four are present. In either case they are so disordered that they cannot be distinguished from the water molecules. The 18 951 unique reflections (Rsym= 0.026) used for structure solution and refinement were recorded with the EMBL imaging‐plate scanner using synchrotron radiation. The structure was solved by Patterson interpretation, locating the three disulfide bridges, followed by tangent phase expansion andE‐Fourier recycling. The anisotropic refinement against allF2data between 1.04 and 10.0 Å resolution by blocked restrained full‐matrix least‐squares techniques converged to a conventionalRindex based onFof 0.084 [I>2a(I) and 10.0>d>1.04 Å] andwR2, the weightedR‐index onF2, of 0.246 (for all data). One peptide molecule adopts a flat β‐sheet structure; the other two possess different irregular backbone conformations, but are similar to each other. All three molecules have a distorted type II′β‐turn around thed‐Trp‐Lys region, but exhibit different side‐chain conformations. The crystal structure is stabilized by a network of inter

ISSN:1399-0047    

DOI:10.1107/S0907444994006104

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

The octapeptide octreotide crystallizes with three peptide molecules and about 20% water in the asymmetric unit, and in many ways possesses diffraction properties similar to those of a `mini‐protein' consisting of 24 amino‐acid residues. It diffracts to about 1.0 Å but data in the range 1.4–1.0 Å are weak. It provides a suitable test of different macromolecular X‐ray data‐collection techniques, especially of their ability to measure weak reflections accurately. In contrast to typical proteins it is possible to perform a full anisotropic refinement, that we believe provides a more objective test of the quality of the data than the internal consistency of equivalent reflections. We have collected a total of six data sets. The X‐ray sources included synchrotron radiation, Cu Kα rotating anodes and Mo Kα sealed tubes; position‐sensitive two‐dimensional detectors from four manufacturers and a four‐circle diffractometer with scintillation counter were employed. Two of the six data sets were collected at low temperature. Reasonable anisotropic refinement was possible with all area‐detector data sets, although significant differences in the precision of the final model were observed. In addition we tested the ability of automated Patterson interpretation to solve the structure using the six independent data sets. The structure solution was only successful using the synchrotron or rotating‐anode data sets,i.e.for the more intense sources. It appears that for structure solution the maximum resolution of the data is critical, whereas for refinement the accur

ISSN:1399-0047    

DOI:10.1107/S0907444994006116

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

Alcohol dehydrogenase prepared fromDrosophila lebanonensisyields well ordered plate‐like crystals which diffract to better than 2.3 Å resolution. The crystals belong to space groupP21of the monoclinic system; the unit‐cell dimensions area= 65.25,b= 55.77,c= 70.02 Å, α = 90, β = 107.08, γ = 90°. The asymmetric unit of the crystal cell is most probably occupied by a dimer, corresponding to a packing density of 2.15 Å3 Da−l. The orientation of the non‐crystallographic twofold symmetry axes is determined by analysis of a self‐rotation function calculated with

ISSN:1399-0047    

DOI:10.1107/S0907444994007353

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY

摘要:

The structure of trypsin from the fungusFusarium oxysporumhas been refined at 1.55 Å resolution by restrained least‐squares minimization to anR‐factor of 14.4%. The data were recorded from a single‐crystal on the X31 beamline at EMBL, Hamburg, using a locally developed image‐plate scanner. The final model consists of 1557 protein atoms, 400 water molecules, one molecule of isopropanol and one monoisopropyl phosphoryl inhibitor group covalently bound to the catalytic Ser195. Comparison of the structure with bovine trypsin reveals significant differences in the active site and suggests a possible explanation for the difference in substrate specificity between the two enzymes. InF. oxysporumtrypsin the specificity pocket is larger than in bovine trypsin. This explains the preference ofF. oxysporumtrypsin for the bulkier arginine over lysine and the reverse preference in bovine trypsin. The binding cavity on the C‐terminal side of the substrate is more restricted inF. oxysporumtrypsin than in mammalian andStreptomyces griseustrypsins, which explains the relative inactivity ofF. oxysporumtrypsin towards peptide–pNA substrate analogues as an unfavourable steric interaction between the side of the binding cavity and thepara‐nitroanilino group of peptide–pNA. The observed restriction of the binding cavity does not lead to a reduced catalytic activity compared

ISSN:1399-0047    

DOI:10.1107/S0907444994009169

出版商:International Union of Crystallography    

年代:1995

数据来源: WILEY