摘要:

An isomorphous derivative of pertussis toxin crystals was prepared using a 2‐α‐mercuric analog ofN‐acetyl neuraminic acid in a method analogous to the use of inhibitors labelled with heavy atoms to solve crystal structures of enzymes. This derivative exploits the specific binding between pertussis toxin and terminal sialic acid residues on receptor glycoproteins. Difference Patterson maps yielded heavy‐atom sites which refined with good statistics, indicating that the protein probably does not undergo a conformational change on receptor binding. Mercuric analogs of other monosaccharides should be easily obtainable using the same synthetic strategy, suggesting a general method for derivatizing crystals of carbohydrate‐bindin

ISSN:1399-0047    

DOI:10.1107/S0907444993009382

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

Chloromuconate cycloisomerase (E.C. 5.5.1.7) is an enzyme involved in the 2,4‐dichlorophenoxyacetate degradation pathway ofAlcaligenes eutrophusJMP134 (pJP4). The crystal structure of this protein was determined at 3 Å resolution by molecular‐replacement techniques using atomic coordinates from the reported crystal structure of the homologous muconate cycloisomerase (E.C. 5.5.1.1) fromPseudomonas putidaas the search model (42% identical positions in the sequences). Structure refinement by simulated‐annealing and restrained least‐squares techniques converged atR= 0.195. In the crystals studied, space groupI4, the protein is present as two octamers per unit cell with two subunits per asymmetric unit. Each subunit consists of two globular domains, one of which forms an α/β‐barrel. Comparison of this structure with that of muconate cycloisomerase reveals the reasons for the altered substrate specificity of chloromuconate cycloisomerase. Marked differences are observed in polarity, accessibility and hydrogen‐bonding potential in the channel leading into the active site as well as in the acti

ISSN:1399-0047    

DOI:10.1107/S090744499300900X

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

Transforming growth factor‐β is a multifunctional cell‐growth regulator and is a member of the TGF‐β superfamily of cytokines. Each monomer is 112 amino acids long and the mature active form is a 25 kDa homodimer. Recently, the crystal structure of TGF‐β2 has been determined independently in two laboratories [Daopin, Piez, Ogawa&Davies (1992).Science,257, 369–373; Schlunegger&Grütter (1992).Nature(London),358, 430–434] and subsequently refined to higher resolutions [Daopin, Li&Davies (1993).Proteins Struct. Funct. Genet.In the press; Schlunegger&Grütter (1993).J. Mol. Biol.In the press]. A detailed structural comparison shows that the two structures are nearly identical with the differences mostly located on the mobile regions of the molecule. The r.m.s. differences between the two structures are 0.10 Å for 104 pairs of Cαatoms, 0.15 Å for 434 pairs of main‐chain atoms, 0.33 Å for 860 out of 890 pairs of protein atoms and a correlation of 90% between the temperatureBfactors of all protein atoms. Based on a comparison of the water molecules, aBvalue of 60.0 Å2is recommended as the cut off for modeling new waters. The structural identity is striking because in one case the material was expressedin vivoin CHO cells whereas in the other case it was expressed inE. coliand had to be refoldedin vitro. The overall coordinate errors are estimated to be 0.21 Å from the Luzzati plot, 0.18 Å from the σAplot, 0.24 Å with Cruickshank's equations and 0.25 Å using the empirical method of Perry&Stroud. These estimates are comparable to the r.m.s. structure superposition. The r.m.s. differences correlate very well with the crystallographicBvalues and the relation is best described with the Cruickshank formula. In addition to the estimation of an overall error, a new application of the Cruickshank formula

ISSN:1399-0047    

DOI:10.1107/S090744499300808X

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

Metal‐substituted crystals of human carbonic anhydrase II belonging to space groupP21with cell dimensionsa= 42.7,b= 41.7,c= 73.0  Å and β = 104.6° were analyzed crystallographically. The resolution limit ranged from 1.82 to 1.92 Å with high completeness (86.2–90.7%). Cobalt(II)‐substituted carbonic anhydrase has a tetrahedral coordination around the metal both at pH 6 and pH 7.8, similar to the native zinc enzyme. In contrast, the catalytically inactive copper(II), nickel(II) and manganese(II) derivatives showed increased coordination number around the metal ion. Whereas the copper is best described as penta‐coordinated, the nickel and manganese are best described as hexa‐coordinated. The results are briefly compared with spectroscopic observations and our current view on carbo

ISSN:1399-0047    

DOI:10.1107/S0907444993008790

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

The molecular structures of the acetate complexes of wild‐type human carbonic anhydrase II (HCAII) and of E106Q mutant human carbonic anhydrase II were solved with high completeness (89–91%) to 2.1 and 1.9 Å resolution, respectively. Both wild‐type and mutant enzyme crystallize in space groupP21with cell dimensionsa= 42.7,b= 41.7,c= 73.0 Å and β = 104.6°. The altered active‐site hydrogen‐bond network caused by the mutation results in a different binding of the inhibitor in the two complexes. In the mutant, but not in the wild‐type complex, a carboxylate O atom is within hydrogen‐bond distance of Thr199 Oγ1. In the wild‐type enzyme ligand hydrogen bonding to this atom is normally only found for hydrogen‐bond donors. The importance of this discrimination on catalysis by the e

ISSN:1399-0047    

DOI:10.1107/S0907444993009667

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

Crystals of bacteriophage Qβ have been obtained by the vapor‐diffusion technique. The crystals diffract to at least 3.5 Å resolution. The crystal space group isC2221with the unit‐cell parametersa= 478,b= 296,c= 477 Å, α = β = γ = 90°. The unit cell contains four virus particles. A pattern of systematic extinctions has been used to deduce the packing of the particles in the cell. A limited data set to 3.9 Å resolution has been collected, and the predicted position has been confirmed by the self‐rotation and the

ISSN:1399-0047    

DOI:10.1107/S0907444993009102

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

摘要:

Affinity‐purified amaryllis lectin was used to grow single crystals using the hanging‐drop method. The space group was found to beC2 with unit‐cell dimensionsa= 73.4 (1),b= 100.3 (1),c= 62.2 (1) Å and β = 137.3 (2)°. Data to 2.25 Å resolution have been recorded and solution of the structure is currently underway by means of molecular‐r

ISSN:1399-0047    

DOI:10.1107/S0907444993009564

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY

ISSN:1399-0047    

DOI:10.1107/S0907444993011400

出版商:International Union of Crystallography    

年代:1994

数据来源: WILEY