Binding and glutathione conjugation of porphyrinogens by plant glutathione transferases

Dixon, D. P., Lapthorn, A. , Madesis, P., Mudd, E. A., Day, A. and Edwards, R. (2008) Binding and glutathione conjugation of porphyrinogens by plant glutathione transferases. Journal of Biological Chemistry, 283(29), pp. 20268-20276. (doi: 10.1074/jbc.M802026200)

Abstract

Overexpression in Escherichia coli of a tau (U) class glutathione transferase (GST) from maize (Zea mays L.), termed ZmGSTU1, caused a reduction in heme levels and an accumulation of porphyrin precursors. This disruption was highly specific, with the expression of the closely related ZmGSTU2 or other maize GSTs having little effect. Expression in E. coli of a series of chimeric ZmGSTU1/ZmGSTU2 proteins identified domains responsible for disrupting porphyrin metabolism. In addition to known heme precursors, expression of ZmGSTU1 led to the accumulation of a novel glutathione conjugate of harderoporphyrin(ogen) (2,7,12,18-tetramethyl-3-vinylporphyrin8,13,17-tripropionic acid). Using the related protoporphyrinogen as a substrate, conjugation could be shown to occur on one vinyl group and was actively catalyzed by the ZmGSTU. In plant transgenesis studies, the ZmGSTUs did not perturb porphyrin metabolism when expressed in the cytosol of Arabidopsis or tobacco. However, expression of a ZmGSTU1-ZmGSTU2 chimera in the chloroplasts of tobacco resulted in the accumulation of the harderoporphyrin(ogen)-glutathione conjugate observed in the expression studies in bacteria. Our results show that the well known ability of GSTs to act as ligand binding(ligandin) proteins of porphyrins in vitro results in highly specific interactions with porphyrinogen intermediates, which can be demonstrated in both plants and bacteria in vivo.

• Item Type: Articles
• Keywords: ACID ANTHOCYANIN SEQUESTRATION ARABIDOPSIS-THALIANA BINDING CHLOROPHYLL conjugation DOMAIN ESCHERICHIA-COLI EXPRESSION GENE FAMILY HEME-BIOSYNTHESIS IN-VITRO IN-VIVO LIGAND LIGANDIN OVEREXPRESSION PRECURSORS PROTEIN PROTEINS REDUCTION S-TRANSFERASE TANDEM MASS-SPECTROMETRY
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Lapthorn, Dr Adrian
• Authors: Dixon, D. P., Lapthorn, A., Madesis, P., Mudd, E. A., Day, A., and Edwards, R.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Biological Chemistry
• Journal Abbr.: J Biol Chem.
• Publisher: American Society for Biochemistry and Molecular Biology, Inc.
• ISSN: 0021-9258
• ISSN (Online): 1083-351X