Structural Basis of the Suppressed Catalytic Activity of Wild-type Human Glutathione Transferase T1-1 Compared to its W234R Mutant

Tars, K.; Larsson, Anna‐Karin; Shokeer, Abeer; Olin, B.; Mannervik, Bengt; Kleywegt, Gerard J.

doi:10.1016/j.jmb.2005.10.049

Cited by 37 publications

(30 citation statements)

References 30 publications

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“…Indeed, the R234W activities with these substrates were still the highest in absolute numbers but just Ͻ3% of the wild type values. On the other hand, some of the naturally occurring GST substrates, such as phenethyl-ITC, (24). H-site residues are marked with gray boxes.…”

Section: Resultsmentioning

confidence: 99%

“…The overlap of the two structures is equally close in the remainder of the polypeptide chains. In the human W234R mutant, Arg 234 displays an ionic bond with the carboxyl group of glutathione (24), and the wild type mouse GST T1-1 presumably forms a similar ionic interaction (Fig. 5A).…”

Section: Minor Structural Modifications Of the C-terminal Helix Causementioning

confidence: 99%

“…The C terminus of GST T1-1 forms a helix that serves as a lid over the active site and brings residues in direct contact with the electrophilic substrate (24). It is assumed that the lid has to open to release the product formed in the catalyzed reaction.…”

Section: Minor Structural Modifications Of the C-terminal Helix Causementioning

confidence: 99%

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Minor Modifications of the C-terminal Helix Reschedule the Favored Chemical Reactions Catalyzed by Theta Class Glutathione Transferase T1-1

Shokeer

Mannervik

2010

Journal of Biological Chemistry

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Adaptive responses to novel toxic challenges provide selective advantages to organisms in evolution. Glutathione transferases (GSTs) play a pivotal role in the cellular defense because they are main contributors to the inactivation of genotoxic compounds of exogenous as well as of endogenous origins. GSTs are promiscuous enzymes catalyzing a variety of chemical reactions with numerous alternative substrates. Despite broad substrate acceptance, individual GSTs display pronounced selectivities such that only a limited number of substrates are transformed with high catalytic efficiency. The present study shows that minor structural changes in the C-terminal helix of mouse GST T1-1 induce major changes in the substrate-activity profile of the enzyme to favor novel chemical reactions and to suppress other reactions catalyzed by the parental enzyme.The molecular evolution of enzyme functions encompasses redesign of existing structures as one of the cornerstones (1). Structural studies and evolutionary analyses give ample examples of structural scaffolds that have been adopted for diverse functions (2). Many enzymes have evolved to acquire high selectivity for naturally occurring substrates, but enzymes involved in the cellular detoxication system generally have a broad substrate acceptance, or promiscuity (3). Proteins have high structural flexibility, and in some enzymes the active site can undergo major conformational changes and thereby accommodate substrates of widely different shapes, as exemplified by cytochrome P450 3A4 (4). Glutathione transferases (GSTs) 2 form a superfamily of enzymes encompassing seven classes of canonical soluble enzymes (5). Some of the GSTs have evolved for intermediary metabolism, such as the biosynthesis of steroid hormones (6) and prostaglandins (7), or the degradation of aromatic acids (8). However, the majority of the soluble GSTs appear to have their primary function in the inactivation of toxic compounds from exogenous as well as endogenous sources.Surprisingly, structurally highly similar GST homologs in the same biological organism or from diverse species differ in their substrate selectivity profiles. A primary determinant for divergent substrate acceptance among GSTs appears to be the H-site, i.e. the binding site for the electrophilic substrate (9, 10). On the other hand, GST A4-4 in rats and mice are structurally quite different from the human counterpart, even though their catalytic efficiencies are similarly evolved for high activity with the cytotoxic 4-hydroxynonenal generated by lipid peroxidation (11). These findings suggest that the GST structure is functionally malleable such that catalytic properties can readily be altered in a relatively short evolutionary time span. In the present investigation we demonstrate how simple point mutations and a deletion in the C-terminal helix of Theta class GST (GST T1-1) can drastically alter the substrate specificity profile with consequent increases in activity with certain substrates and decreases with other substrates. This shi...

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Section: Resultsmentioning

confidence: 99%

Section: Minor Structural Modifications Of the C-terminal Helix Causementioning

confidence: 99%

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Minor Modifications of the C-terminal Helix Reschedule the Favored Chemical Reactions Catalyzed by Theta Class Glutathione Transferase T1-1

Shokeer

Mannervik

2010

Journal of Biological Chemistry

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“…The structure of human GST T1-1 has been determined [Tars et al, 2006], which allows interpretation of the results of the mutations (Fig. 6).…”

Section: Discussionmentioning

confidence: 99%

Screening and characterization of variant Theta‐class glutathione transferases catalyzing the activation of ethylene dibromide to a mutagen

Josephy

Taylor

Vervaet

et al. 2006

Environ and Mol Mutagen

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Ethylene dibromide (EDB) is a widespread environmental pollutant and mutagen/carcinogen. Certain Theta-class glutathione transferases (GSTs), enzymes that catalyze the reaction of reduced glutathione (GSH) with electrophiles, activate EDB to a mutagen. Previous studies have shown that human GST T1-1, but not rat GST T2-2, activates EDB. We have constructed an E. coli lacZ reversion mutagenicity assay system in which expression of recombinant GST supports activation of EDB to a mutagen. Hexa-histidine N-terminal tagging of GST T1-1 results in greatly enhanced expression of the recombinant enzyme and gives a lacZ strain that shows a mutagenic response to EDB at extremely low levels (approximately 1 ng EDB per plate). The hexa-histidine-tagged enzyme was purified in one step by Ni(2+)-affinity chromatography. We applied the lacZ mutagenicity assay to the rapid screening of a library of variant GST Theta enzymes. Sequence variants with altered catalytic activities were identified, purified, and characterized.

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“…The homodimer GST isozymes present in human is given in Fig. 3 where the ribbon diagrams for the crystal structures were adapted from Protein DataBank with accession numbers 1PKW for GST A1-1; 11GS for GST P1-1; 1YJ6 for GST M1-1; 2C3N for GST T1-1; 1YZX for GST K1-1; 1EEM for GST O1-1; 1FW1 for GST Z1-1; 2H8A for MGST-1 (Oakley et al, 1997;Board et al, 2000;Polekhina et al, 2001;Li et al, 2005;Grahn et al, 2006;Holm et al, 2006;Tars et al, 2006;Patskovsky et al, 2009). …”

Section: Structural and Functional Properties Of Glutathione Transfermentioning

confidence: 99%

Kinases and glutathione transferases: selective and sensitive targeting

Isgor

2011

Front. Biol.

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Kinases, representing almost 500 proteins in the human genome, are responsible for catalyzing the phosphorylation reaction of amino acid residues at their targets. As the largest family of kinases, the protein tyrosine kinases (PTKs) have roles in controlling the essential cellular activities, and their deregulation is generally related to pathologic conditions. The recent efforts on identifying their signal transducer or mediator role in cellular signaling revealed the interaction of PTKs with numerous enzymes of different classes, such as Ser/Thr kinases (STKs), glutathione transferases (GSTs), and receptor tyrosine kinases (RTKs). In either regulation or enhancing the signaling, PTKs are determined in close interaction with these enzymes, under specific cellular conditions, such as oxidative stress and inflammation. In this concept, intensive research on thiol metabolizing enzymes recently showed their involvement in the physiologic functions in cellular signaling besides their well known traditional role in antioxidant defense. The shared signaling components between PTK and GST family enzymes will be discussed in depth in this research review to evaluate the results of recent studies important in drug targeting for therapeutic intervention, such as cell viability, migration, differentiation and proliferation.

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Structural Basis of the Suppressed Catalytic Activity of Wild-type Human Glutathione Transferase T1-1 Compared to its W234R Mutant

Cited by 37 publications

References 30 publications

Minor Modifications of the C-terminal Helix Reschedule the Favored Chemical Reactions Catalyzed by Theta Class Glutathione Transferase T1-1

Minor Modifications of the C-terminal Helix Reschedule the Favored Chemical Reactions Catalyzed by Theta Class Glutathione Transferase T1-1

Screening and characterization of variant Theta‐class glutathione transferases catalyzing the activation of ethylene dibromide to a mutagen

Kinases and glutathione transferases: selective and sensitive targeting

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