Reference "Structures of herbicides in complex with their detoxifying enzyme glutathione S-transferase - explanations for the selectivity of the enzyme in plants"

Reference ID

7214

Title

Structures of herbicides in complex with their detoxifying enzyme glutathione S-transferase - explanations for the selectivity of the enzyme in plants

Source

Structure (London, England), 1998, vol. 6, pp. 1445-1452

Authors (3)

Prade-L	Huber-R
Bieseler-B

Abstract

BACKGROUND: Glutathione S-transferases (GSTs) are detoxifying enzymes present in
all aerobic organisms. These enzymes catalyse the conjugation of glutathione
with a variety of electrophilic compounds. In plants, GSTs catalyse the first
step in the degradation of several herbicides, such as triazines and acetamides,
thus playing an important role in herbicide tolerance. RESULTS: We have solved
the structures of GST-I from maize in complex with an atrazine-glutathione
conjugate (at 2.8 A resolution) and GST from Arabidopsis thaliana (araGST) in
complex with an FOE-4053-glutathione conjugate (at 2.6 A resolution). These
ligands are products of the detoxifying reaction and are well defined in the
electron density. The herbicide-binding site (H site) is different in the two
structures. The architecture of the glutathione-binding site (G site) of araGST
is different to that of the previously described structure of GST in complex
with two S-hexylglutathione molecules, but is homologous to that of GST-I.
CONCLUSIONS: Three features are responsible for the differences in the H site of
the two GSTs described here: the exchange of hydrophobic residues of different
degrees of bulkiness; a slight difference in the location of the H site; and a
difference in the degree of flexibility of the upper side of the H site, which
is built up by the loop between helices alpha4 and alpha5. Taking these two
structures as a model, the different substrate specificities of other plant GSTs
may be explained. The structures reported here provide a basis for the design of
new, more selective herbicides.