scholarly journals Bivalent cations stabilize yeast alcohol dehydrogenase I

1997 ◽  
Vol 323 (2) ◽  
pp. 409-413 ◽  
Author(s):  
Xavier De BOLLE ◽  
Carla VINALS ◽  
Jacques FASTREZ ◽  
Ernest FEYTMANS
Keyword(s):  
Alcohol Dehydrogenase ◽  
Protein Unfolding ◽  
Three Dimensional ◽  
Reduced Form ◽  
Electrostatic Repulsion ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Yeast Alcohol Dehydrogenase ◽  
Bivalent Cations

The thermostability of yeast alcohol dehydrogenase (ADH) I is strongly dependent on the presence of NaCl, a salt that is almost neutral on the Hofmeister scale, which suggests that solvent-accessible electrostatic repulsion might play a role in the inactivation of the enzyme. Moreover, CaCl2 and MgCl2 are able to stabilize the enzyme at millimolar concentrations. Ca2+ stabilizes yeast ADH I by preventing the dissociation of the reduced form of the enzyme and by preventing the unfolding of the oxidized form of the enzyme. An analysis of several chimaeric ADHs suggests that Ca2+ is fixed by the Asp-236 and Glu-101 side chains in yeast ADH I, but that Ca2+ can be displaced by replacing Met-168 by an Arg residue, as suggested by a three-dimensional model of the enzyme structure. These results indicate that electrostatic repulsion can cause protein unfolding and/or dissociation. It is proposed that yeast ADH I binds Mg2+in vivo.

scholarly journals Amino acids important in enzyme activity and dimer stability for Drosophila alcohol dehydrogenase

1995 ◽  
Vol 308 (2) ◽  
pp. 419-423 ◽  
Author(s):  
S W Chenevert ◽  
N G Fossett ◽  
S H Chang ◽  
I Tsigelny ◽  
M E Baker ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Alcohol Dehydrogenase ◽  
Binding Site ◽  
Aspartic Acid ◽  
Three Dimensional ◽  
Side Chain ◽  
Wild Type ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Substrate Binding Site

We have determined the nucleotide sequences of eight ethyl methanesulphonate-induced mutants in Drosophila alcohol dehydrogenase (ADH), of which six were previously characterized by Hollocher and Place [(1988) Genetics 116, 253-263 and 265-274]. Four of these ADH mutants contain a single amino acid change: glycine-17 to arginine, glycine-93 to glutamic acid, alanine-159 to threonine, and glycine-184 to aspartic acid. Although these mutants are inactive, three mutants (Gly17Arg, Gly93Glu and Gly184Asp) form stable homodimers, as well as heterodimers with wild-type ADH, in which the wild-type ADH subunit retains full enzyme activity [Hollocher and Place (1988) Genetics 116, 265-274]. Interestingly, the Ala159Thr mutant does not form either stable homodimers or heterodimers with wild-type ADH, suggesting that alanine-159 is important in stabilizing ADH dimers. The mutations were analysed in terms of a three-dimensional model of ADH using bacterial 20 beta-hydroxysteroid dehydrogenase and rat dihydropteridine reductase as templates. The model indicates that mutations in glycine-17 and glycine-93 affect the binding of NAD+. It also shows that alanine-159 is part of a hydrophobic anchor on the dimer interface of ADH. Replacement of alanine-159 with threonine, which has a larger side chain and can hydrogen bond with water, is likely to reduce the strength of the hydrophobic interaction. The three-dimensional model shows that glycine-184 is close to the substrate binding site. Replacement of glycine-184 with aspartic acid is likely to alter the position of threonine-186, which we propose hydrogen bonds to the carboxamide moiety of NAD+. Also, the negative charge on the aspartic acid side chain may interact with the substrate and/or residues in the substrate binding site. These mutations provide information about ADH catalysis and the stability of dimers, which may also be useful in understanding homologous dehydrogenases, which include the human 17 beta-hydroxysteroid, 11 beta-hydroxysteroid and 15-hydroxyprostaglandin dehydrogenases.

scholarly journals Mutagenesis and Molecular Modeling Reveal Three Key Extracellular Loops of the Membrane Receptor HasR That Are Involved in Hemophore HasA Binding

2007 ◽  
Vol 189 (14) ◽  
pp. 5379-5382 ◽  
Author(s):  
Clément Barjon ◽  
Karine Wecker ◽  
Nadia Izadi-Pruneyre ◽  
Philippe Delepelaire
Keyword(s):  
Molecular Modeling ◽  
Outer Membrane ◽  
Three Dimensional ◽  
Membrane Receptor ◽  
Dimensional Model ◽  
Outer Membrane Receptor ◽  
Three Dimensional Model ◽  
Extracellular Loops

ABSTRACT On the basis of the three-dimensional model of the heme/hemophore TonB-dependent outer membrane receptor HasR, mutants with six-residue deletions in the 11 putative extracellular loops were generated. Although all mutants continued to be active TonB-dependent heme transporters, mutations in three loops abolished hemophore HasA binding both in vivo and in vitro.

Three-Dimensional Model for Virtual Surgical Simulation, during Complex Skull Base Surgery and Aneurysm Surgery

Skull Base ◽  
2008 ◽  
Vol 18 (S 01) ◽  
Author(s):  
Akio Morita ◽  
Toshikazu Kimura ◽  
Shigeo Sora ◽  
Kengo Nishimura ◽  
Hisayuki Sugiyama ◽  
...  
Keyword(s):  
Skull Base ◽  
Surgical Simulation ◽  
Skull Base Surgery ◽  
Three Dimensional ◽  
Aneurysm Surgery ◽  
Dimensional Model ◽  
Three Dimensional Model
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