Insights into ligand-induced conformational change in Cel5A from Bacillus agaradhaerens revealed by a catalytically active crystal form

2000 ◽  
Vol 297 (3) ◽  
pp. 819-828 ◽  
Author(s):  
Annabelle Varrot ◽  
Martin Schülein ◽  
Gideon J Davies
Keyword(s):  
Conformational Change ◽  
Crystal Form ◽  
Active Crystal ◽  
Catalytically Active ◽  
Bacillus Agaradhaerens

Use of conformationally restricted pyridinium α-D-N-acetylneuraminides to probe specificity in bacterial and viral sialidases

2005 ◽  
Vol 83 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Jacqueline N Watson ◽  
Tara L Knoll ◽  
Johnny H Chen ◽  
Doug T.H Chou ◽  
Thor J Borgford ◽  
...  
Keyword(s):  
Conformational Change ◽  
Conformationally Restricted ◽  
Rate Determining Step ◽  
Bacterial Enzyme ◽  
Catalytically Active ◽  
High Sequence Homology ◽  
Catalytic Mechanisms ◽  
Different Origins ◽  
Leaving Group Ability ◽  
Single Enzyme

Investigations into subtle changes in the catalytic activity of sialidases have been performed using enzymes from several different origins, and their results have been compared. This work highlights the potential pitfalls encountered when extending conclusions derived from mechanistic studies on a single enzyme even to those with high-sequence homology. Specifically, a panel of 5 pyridinium N-acetylneuraminides were used as substrates in a study that revealed subtle differences in the catalytic mechanisms used by 4 different sialidase enzymes. The lowest reactivity towards the artificial (pyridinium) substrates was displayed by the Newcastle disease virus hemagglutinin-neuraminidase. Moreover, in reactions involving aryl N-acetylneuraminides, the activity of the Newcastle enzyme was competitively inhibited by the 3,4-dihydro-2H-pyrano[3,2-c]pyridinium compound with a Ki = 58 µmol/L. Alternatively, the 3 bacterial enzymes tested, from Salmonella typhimurium, Clostridium perfringens, and Vibrio cholerae, were catalytically active against all members of the panel of substrates. Based on the observed effect of leaving-group ability, it is proposed that the rate-determining step for kcat (and likely for kcat/Km as well) with each bacterial enzyme is as follows: sialylation, which is concerted with conformational change for V. cholerae; and conformational change for S. typhimurium and C. perfringens.Key words: sialidases, neuraminidases, sialic acids, glycosidase, mechanism.

scholarly journals H.p.l.c. separation and study of the charge isomers of human placental glutathione transferase

1986 ◽  
Vol 239 (1) ◽  
pp. 53-57 ◽  
Author(s):  
L L Radulovic ◽  
A P Kulkarni
Keyword(s):  
Conformational Change ◽  
Glutathione Transferase ◽  
Tissue Concentration ◽  
Polyacrylamide Gel Electrophoresis ◽  
Kinetic Studies ◽  
Anionic Form ◽  
Net Charge ◽  
Catalytically Active ◽  
Low Activity

Glutathione transferase (GST) from human placenta was purified by affinity chromatography and anion-exchange h.p.l.c. The enzyme exhibited different chromatographic and electrophoretic behaviours according to the concentration of GSH, suggesting a possible change in the net charge of the molecule and a concomitant conformational change due to ligand binding. Two interconvertible forms were quantitatively separated into distinct catalytically active states by h.p.l.c. Depending upon the GSH concentration, polyacrylamide-gel electrophoresis revealed the presence of one or two bands. A Kd of 0.42 mM for GSH was determined fluorimetrically. The loss in intrinsic fluorescence also suggested a conformational change in the enzyme. Kinetic studies using ethacrynic acid were conducted to determine whether the presumed conformational change could effect the catalytic capability of placental GST. A biphasic response in initial velocities was observed with increasing concentrations of GSH. Two apparent Km values of 0.38 and 50.27 mM were obtained for GSH, whereas Vmax. values showed a 46-fold difference. It was concluded that the enzyme assumes a highly anionic form in the presence of a low GSH concentration, whereas it is converted into relatively weaker anionic form when its immediate environment contains a high GSH concentration. Since the average tissue concentration of total GSH was estimated at 0.11 mM for term placenta, the results suggest that the high-affinity-low-activity conformer would predominate in vivo.

The structure of dihydrodipicolinate reductase (DapB) fromMycobacterium tuberculosisin three crystal forms

2009 ◽  
Vol 66 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Robert Janowski ◽  
Georgia Kefala ◽  
Manfred S. Weiss
Keyword(s):  
Conformational Change ◽  
Normal Modes ◽  
Low Frequency ◽  
Pyridine Nucleotide ◽  
Crystal Form ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Crystal Forms ◽  
Comparison Of The Results ◽  
Unstable Product

Dihydrodipicolinate reductase (DHDPR, DapB) is an enzyme that belongs to the L-lysine biosynthetic pathway. DHDPR reduces the α,β-unsaturated cyclic imine 2,3-dihydrodipicolinic acid to yield the compound 2,3,4,5-tetrahydrodipicolinic acid in a pyridine nucleotide-dependent reaction. The substrate of this reaction is the unstable product of the preceding enzyme dihydrodipicolinate synthase (DHDPS, DapA). Here, the structure of apo-DHDPR fromMycobacterium tuberculosisis reported in two orthorhombic crystal forms, as well as the structure of DHDPR fromM. tuberculosisin complex with NADH in a monoclinic crystal form. A comparison of the results with previously solved structures of this enzyme shows that DHDPR undergoes a major conformational change upon binding of its cofactor. This conformational change can be interpreted as one of the low-frequency normal modes of the structure.

The native structure of the eukaryotic ribosome

1983 ◽  
Vol 41 ◽  
pp. 432-433
Author(s):  
R.A. Milligan ◽  
P.N.T. Unwin
Keyword(s):  
Ribosomal Proteins ◽  
Crystal Form ◽  
Native Structure ◽  
X Ray Diffraction ◽  
Eukaryotic Ribosome ◽  
Vitro Analysis ◽  
In Vitro Analysis ◽  
Resolution Structure ◽  
Stable Unit

A detailed understanding of the mechanism of protein synthesis will ultimately depend on knowledge of the native structure of the ribosome. Towards this end we have investigated the low resolution structure of the eukaryotic ribosome embedded in frozen buffer, making use of a system in which the ribosomes crystallize naturally.The ribosomes in the cells of early chicken embryos form crystalline arrays when the embryos are cooled at 4°C. We have developed methods to isolate the stable unit of these arrays, the ribosome tetramer, and have determined conditions for the growth of two-dimensional crystals in vitro, Analysis of the proteins in the crystals by 2-D gel electrophoresis demonstrates the presence of all ribosomal proteins normally found in polysomes. There are in addition, four proteins which may facilitate crystallization. The crystals are built from two oppositely facing P4 layers and the predominant crystal form, accounting for >80% of the crystals, has the tetragonal space group P4212, X-ray diffraction of crystal pellets demonstrates that crystalline order extends to ~ 60Å.

Growth of Catalytically Active Nanostructures in the Nonequilibrium Epitaxy Regime

2015 ◽  
Vol 60 (6) ◽  
pp. 546-552
Author(s):  
V.M. Gorshkov ◽  
◽  
V.V. Kuzmenko
Keyword(s):  
Catalytically Active

A Possible Basis for Nondestructive Characterization of Ropes of Nylon 6

1997 ◽  
Vol 503 ◽  
Author(s):  
H. Jiang ◽  
M. K. Davis ◽  
R. K. Eby ◽  
P. Arsenovic
Keyword(s):  
Tensile Strength ◽  
Service Life ◽  
Fiber Diameter ◽  
Structural Parameters ◽  
Crystal Form ◽  
Nylon 6 ◽  
Remaining Service Life ◽  
Nondestructive Characterization ◽  
Fractional Content

ABSTRACTPhysical properties and structural parameters have been measured for ropes of nylon 6 as a function of the number of use operations. The fractional content of the α crystal form, sound velocity, birefringence, tensile strength and length all increase systematically and significantly with increasing the number of use operations. The fractional content of the γ crystal form and fiber diameter decrease with use. These trends indicate that the measurement of such properties and structural parameters, especially the length, provide a possible basis for establishing a reliable, rapid, and convenient nondestructive characterization method to predict the remaining service life of nylon 6 ropes.

Sign in / Sign up

Export Citation Format

Share Document