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In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
Published on: August 20, 2019
Quantitative structural insight into human variegate porphyria disease
Baifan Wang1, Xin Wen, Xiaohong Qin
1State Key Laboratory of Elemento-Organic Chemistry, Department of Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China.
The Journal of Biological Chemistry
|March 8, 2013
Summary
Defects in the human protoporphyrinogen oxidase (hPPO) gene cause variegate porphyria (VP). This study reveals that VP mutations disrupt hPPO
Area of Science:
- Biochemistry
- Structural Biology
- Genetics
Background:
- Variegate porphyria (VP) is a dominantly inherited disorder caused by defects in the human protoporphyrinogen oxidase (hPPO) gene.
- These genetic defects lead to a significant decrease in hPPO enzymatic activity, impacting heme biosynthesis.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying VP by investigating VP-causing hPPO mutants.
- To correlate structural changes with altered enzymatic activity.
Main Methods:
- Site-directed mutagenesis and expression of hPPO mutants.
- Biochemical assays to determine enzymatic activity (kcat/Km).
- X-ray crystallography to obtain high-resolution structures of mutants.
- Molecular dynamics simulations and statistical analysis to assess conformational dynamics.
Main Results:
- Crystal structures of R59Q and R59G hPPO mutants were determined, showing minimal static structural differences from wild-type.
- Molecular dynamics simulations revealed that VP-causing mutations impair the ability of hPPO to adopt privileged conformations.
- A strong correlation (R² > 0.9) was found between the probability of privileged conformations and catalytic efficiency (kcat/Km).
- The catalytic activity of 44 reported VP mutants was accurately predicted based on conformational sampling.
Conclusions:
- VP-causing mutations affect hPPO catalytic activity by altering its conformational dynamics, rather than causing significant static structural changes.
- The study provides quantitative structural insights into the molecular basis of human VP.
- This approach accurately predicts mutant activity, aiding in understanding disease mechanisms.
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