Specific features and assembly of the plant mitochondrial complex I revealed by cryo-EM

Heddy Soufari,Yaser Hashem,Florent Waltz,Camila Parrot,Lauriane Kuhn

doi:10.1038/s41467-020-18814-w

Abstract

Mitochondria are the powerhouses of eukaryotic cells and the site of essential metabolic reactions. Complex I or NADH:ubiquinone oxidoreductase is the main entry site for electrons into the mitochondrial respiratory chain and constitutes the largest of the respiratory complexes. Its structure and composition vary across eukaryote species. However, high resolution structures are available only for one group of eukaryotes, opisthokonts. In plants, only biochemical studies were carried out, already hinting at the peculiar composition of complex I in the green lineage. Here, we report several cryo-electron microscopy structures of the plant mitochondrial complex I. We describe the structure and composition of the plant respiratory complex I, including the ancestral mitochondrial domain composed of the carbonic anhydrase. We show that the carbonic anhydrase is a heterotrimeric complex with only one conserved active site. This domain is crucial for the overall stability of complex I as well as a peculiar lipid complex composed of cardiolipin and phosphatidylinositols. Moreover, we also describe the structure of one of the plant-specific complex I assembly intermediates, lacking the whole PD module, in presence of the maturation factor GLDH. GLDH prevents the binding of the plant specific P1 protein, responsible for the linkage of the PP to the PD module.

Highlights

Mitochondria are the powerhouses of eukaryotic cells and the site of essential metabolic reactions
In order to obtain a high-resolution structure of the plant mitochondrial complex I and its additional subunits, we purified mitochondria from Brassica oleracea var. botrytis, a close relative to the model plant Arabidopsis, as previously described[12]
The plant mitochondrial complex I has the classical open L-shape formed by the matrix and membrane arms (Fig. 1)

Summary

Introduction

Mitochondria are the powerhouses of eukaryotic cells and the site of essential metabolic reactions. In order to obtain a high-resolution structure of the plant mitochondrial complex I and its additional subunits, we purified mitochondria from Brassica oleracea var. After particle sorting (see “Methods” section) we obtained cryo-EM reconstructions of two main complex I states: the full plant mitochondrial complex I, as well as reconstruction of a complex I assembly intermediate, without the PD module, and with the plant-specific assembly factor GLDH13 (Supplementary Fig. 1).

Results

Conclusion