Structural insight into the type-II mitochondrial NADH dehydrogenases

Area of Science:

• Biochemistry
• Structural Biology
• Mitochondrial Physiology

Background:

• Type-II NADH dehydrogenases (NDH-2s) are essential alternatives to Complex I in the mitochondrial respiratory chain.
• Yeast NDH-2 (Ndi1) maintains mitochondrial NADH/NAD(+) homeostasis and is a potential therapeutic for Complex I-deficient diseases like Parkinson's.
• NDH-2s in pathogens are promising targets for novel antibiotics.

Purpose of the Study:

• To elucidate the catalytic mechanism of NDH-2s by determining the crystal structures of yeast Ndi1.
• To understand the structural basis for Ndi1's activity, membrane targeting, and substrate binding.

Main Methods:

• X-ray crystallography was used to solve the structures of Ndi1 in various substrate-bound states.
• Biochemical assays were employed to assess the role of homodimerization and ubiquinone-binding sites.

Main Results:

• Ndi1 homodimerization is critical for catalytic activity and membrane localization.
• Two ubiquinone-binding sites (UQ(I) and UQ(II)) were identified.
• NADH and UQ(I) can bind simultaneously, with UQ(I) likely acting as an intermediate for electron transfer to UQ(II) via FAD.

Conclusions:

• The study reveals the regulatory and catalytic mechanisms of Ndi1.
• These findings may facilitate the development and targeting of NDH-2s for therapeutic applications and antibiotic strategies.