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Molecular characterization of a novel His333Arg variant of human protoporphyrinogen oxidase IX.

Abstract
Variegate porphyria is caused by mutations in the protoporphyrinogen oxidase IX (PPOX, EC 1.3.3.4) gene, resulting in reduced overall enzymatic activity of PPOX in human tissues. Recently, we have identified the His333Arg mutation in the PPOX protein (PPOX(H333R)) as a putative founder mutation in the Moroccan Jewish population. Herein we report the molecular characterization of PPOX(H333R) in vitro and in cells. Purified recombinant PPOX(H333R) did not show any appreciable enzymatic activity in vitro, corroborating the clinical findings. Biophysical experiments and molecular modeling revealed that PPOX(H333R) is not folded properly and fails to adopt its native functional three-dimensional conformation due to steric clashes in the vicinity of the active site of the enzyme. On the other hand, PPOX(H333R) subcellular distribution, as evaluated by live-cell confocal microscopy, is unimpaired suggesting that the functional three-dimensional fold is not required for efficient transport of the polypeptide chain into mitochondria. Overall, the data presented here provide molecular underpinnings of the pathogenicity of PPOX(H333R) and might serve as a blueprint for deciphering whether a given PPOX variant represents a disease-causing mutation.
AuthorsZora Novakova, Jana Mikesova, Marketa Ondrakova, Zsofia Kutil, Katerina Vesela, Pavel Martasek, Cyril Barinka
JournalBiochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 588 Pg. 182-186 (01 15 2022) ISSN: 1090-2104 [Electronic] United States
PMID34968794 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
CopyrightCopyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.
Chemical References
  • Flavoproteins
  • Mitochondrial Proteins
  • PPOX protein, human
  • Protoporphyrinogen Oxidase
Topics
  • Amino Acid Sequence
  • Biophysical Phenomena
  • Cell Line
  • Enzyme Stability
  • Flavoproteins (chemistry, genetics, isolation & purification)
  • Humans
  • Kinetics
  • Mitochondrial Proteins (chemistry, genetics, isolation & purification)
  • Models, Molecular
  • Mutation (genetics)
  • Protein Multimerization
  • Protoporphyrinogen Oxidase (chemistry, genetics, isolation & purification)
  • Subcellular Fractions (metabolism)
  • Temperature

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