ATP synthase hexamer assemblies shape cristae of Toxoplasma mitochondria

Abstract

Mitochondrial ATP synthase plays a key role in inducing membrane curvature to establish cristae. In Apicomplexa causing diseases such as malaria and toxoplasmosis, an unusual cristae morphology has been observed, but its structural basis is unknown. Here, we report that the apicomplexan ATP synthase assembles into cyclic hexamers, essential to shape their distinct cristae. Cryo-EM was used to determine the structure of the hexamer, which is held together by interactions between parasite-specific subunits in the lumenal region. Overall, we identified 17 apicomplexan-specific subunits, and a minimal and nuclear-encoded subunit-a. The hexamer consists of three dimers with an extensive dimer interface that includes bound cardiolipins and the inhibitor IF1. Cryo-ET and subtomogram averaging revealed that hexamers arrange into ~20-megadalton pentagonal pyramids in the curved apical membrane regions. Knockout of the linker protein ATPTG11 resulted in the loss of pentagonal pyramids with concomitant aberrantly shaped cristae. Together, this demonstrates that the unique macromolecular arrangement is critical for the maintenance of cristae morphology in Apicomplexa.

Composition and stage dynamics of mitochondrial complexes in Plasmodium falciparum

“…5a). The fraction unable to enter the gel potentially represents higher oligomeric CV states, while we interpret the~2.2 MDa band as the unusually large CV dimer, both of which were recently identified in T. gondii 61 . This is based on a stoichiometry of 10 ATPc subunits for the c-ring, canonical stoichiometry for orthologues to known components and single copies of novel components, predicting a monomer mass of~1 MDa (Table 1).…”

Complexome profile of Toxoplasma gondii mitochondria identifies divergent subunits of respiratory chain complexes including new subunits of cytochrome bc1 complex

“…members of this complex (Figs 2D and S2D). Indeed, these three proteins were identified in a recent structure of Toxoplasma ATP synthase [41] and were named ATPTG1, ATPTG7 and ATPTG16, respectively. Homology searches with the HMMER tool suggests they have a similar phylogenetic distribution to recently discovered myzozoan-restricted ATP synthase subunits [6,18] (S4B Fig and S7 Table), highlighting the divergence of the ATP synthase complex in this lineage.…”

“…A line where ribosomal protein mS35 is downregulated was used as positive control for loss of complex IV [34]. [41]. Interestingly, TGGT1_246540 appears to encodes both the ATP synthase subunit ATPTG1 and the complex III subunit CytC1.…”

“…Likewise, in eight IP experiments for complex III that we performed (five using CytC1, and two using Rieske, as baits) only C-terminal peptides of TGGT1_246540, from the portion of the protein predicted to encode the complex III subunit CytC1, are identified (S11 Table). Finally, the atomic model of ATP synthase resolved only the N-terminal 153aa of ATPTG1 as part of the structure [41]. The ATPTG1 subunit appears myzozoan-specific but is only fused to a cytochrome c 1 domain in a phylogenetically restricted group of apicomplexans.…”

Supramolecular associations between atypical oxidative phosphorylation complexes of Euglena gracilis

“…The angle formed between the CV membrane sector (F O ) of the two monomers in Euglena dimer is much lower (40°) than in the dimers of opisthokonts (70°), so the effect of these dimers on cristae shape might be different. In this respect, lamellar cristae are found in the supergroup of opisthokonts, while tubular-shaped cristae typify the unicellular supergroup SAR, containing stramenopiles, alveolates, and rhizarians (Mühleip et al 2016(Mühleip et al , 2021. Euglenids, members of the protistan supergroup Excavata, generally have discoidal cristae, which exhibit a paddle-like morphology (Kaurov et al 2018).…”