Evolution of Negative Cooperativity in Glutathione Transferase Enabled Preservation of Enzyme Function.
Negative cooperativity in enzyme reactions, in which the first event makes subsequent events less favorable, is sometimes well understood at the molecular level, but its physiological role has often been obscure. Negative cooperativity occurs in human glutathione transferase (GST) GSTP1-1 when it binds and neutralizes a toxic nitric oxide adduct, the dinitrosyl-diglutathionyl iron complex (DNDGIC). However, the generality of this behavior across the divergent GST family and its evolutionary significance were unclear. To investigate, we studied 16 different GSTs, revealing that negative cooperativity is present only in more recently evolved GSTs, indicating evolutionary drift in this direction. In some variants, Hill coefficients were close to 0.5, the highest degree of negative cooperativity commonly observed (although smaller values of nHare theoretically possible). As DNDGIC is also a strong inhibitor of GSTs, we suggest negative cooperativity might have evolved to maintain a residual conjugating activity of GST against toxins even in the presence of high DNDGIC concentrations. Interestingly, two human isoenzymes that play a special protective role, safeguarding DNA from DNDGIC, display a classical half-of-the-sites interaction. Analysis of GST structures identified elements that could play a role in negative cooperativity in GSTs. Beside the well known lock-and-key and clasp motifs, other alternative structural interactions between subunits may be proposed for a few GSTs. Taken together, our findings suggest the evolution of self-preservation of enzyme function as a novel facility emerging from negative cooperativity.
From the Department of Chemical Sciences and Technologies.
Alessio
A
Bocedi
From the Department of Chemical Sciences and Technologies.
Raffaele
R
Fabrini
Department of Biology, and.
Mario
M
Lo Bello
Department of Experimental Medicine and Surgery, University of Rome, Tor Vergata, Rome 00133, Italy.
Anna Maria
AM
Caccuri
From the Department of Chemical Sciences and Technologies.
Giorgio
G
Federici
Department of Neurochemistry, Stockholm University SE-10691 Stockholm, Sweden, and.
Bengt
B
Mannervik
Aix Marseille Université, CNRS, Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, 13009 Marseille, France.
Athel
A
Cornish-Bowden
From the Department of Chemical Sciences and Technologies, riccig@uniroma2.it.
Giorgio
G
Ricci
D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005296:Ferrous Compounds / Q000494:pharmacology*; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D005982:Glutathione Transferase / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D009569:Nitric Oxide / Q000378:metabolism*
D005296:Ferrous Compounds; C404202:dinitrosylbis(glutathione)iron(II); D009569:Nitric Oxide; D005982:Glutathione Transferase; D005978:Glutathione
enzyme; enzyme inactivation; enzyme kinetics; enzyme mechanism; enzyme structure