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Effect of N-terminal alpha-helix formation on the dimerization and intracellular targeting of alanine : glyoxylate aminotransferase

Lumb, MJ; Drake, AF; Danpure, CJ; (1999) Effect of N-terminal alpha-helix formation on the dimerization and intracellular targeting of alanine : glyoxylate aminotransferase. J BIOL CHEM , 274 (29) 20587 - 20596. Gold open access

Abstract

The unparalleled peroxisome-to-mitochondrion mistargeting of alanine:glyoxylate aminotransferase (AGT) in the hereditary disease primary hyperoxaluria type 1 is caused by the combined presence of a common Pro(11) --> Leu polymorphism and a disease-specific Gly(170) --> Arg mutation. The Pro(11) --> Leu replacement generates a functionally weak N-terminal mitochondrial targeting sequence (MTS), the efficiency of which is increased by the additional presence of the Gly(170) --> Arg replacement. AGT dimerization is inhibited in the combined presence of both replacements but not when each is present separately. In this paper we have attempted to identify the structural determinants of AGT dimerization and mitochondrial mistargeting, Unlike most MTSs, the polymorphic MTS of AGT has little tendency to adopt an alpha-helical conformation in vitro. Nevertheless, it is able to target efficiently a monomeric green fluorescent (GFP) fusion protein, but not dimeric AGT, to mitochondria in transfected COS-1 cells. Increasing the propensity of this RIFTS to fold into an alpha-helix, by making a double Pro(11) --> Leu + Pro(10) --> Leu replacement, enabled it to target both GFP and AGT efficiently to mitochondria. The double Pro(11) --> Leu + Pro(10) --> Leu replacement retarded AGT dimerization in vitro as did the disease-causing double Pro(11) --> Leu + Gly(170) --> Arg replacement. These data suggest that N-terminal alpha-helix formation is more important for maintaining AGT in a conformation (ie. monomeric) compatible with mitochondrial import than it is for the provision of mitochondrial targeting information. The parallel effects of the Pro(10) --> Leu and Gly(170) --> Arg replacements on the dimerization and intracellular targeting of polymorphic AGT (containing the Pro(11) --> Leu replacement) raise the possibility that they might achieve their effects by the same mechanism.

Type: Article
Title: Effect of N-terminal alpha-helix formation on the dimerization and intracellular targeting of alanine : glyoxylate aminotransferase
Open access status: An open access publication
Publisher version: http://www.jbc.org/content/early/recent/0
Keywords: GREEN FLUORESCENT PROTEIN, PRIMARY HYPEROXALURIA TYPE-1, MITOCHONDRIAL ASPARTATE-AMINOTRANSFERASE, LIVER ALDEHYDE DEHYDROGENASE, RAT-LIVER, PEROXISOMAL LOCALIZATION, STRUCTURAL FEATURES, PRECURSOR PROTEINS, MAMMALIAN-CELLS, SIGNAL PEPTIDE
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/96230
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