Image of the Day: Unusual ATP Synthase

A single-celled organism has an energy-producing enzyme with unique features.

Emily Makowski
Jan 8, 2020
Reconstruction of E. gracilis ATP synthase

Found inside mitochondria, ATP synthase generates the energy storage molecule adenosine triphosphate, which the cells of all living things use for fuel. The enzyme generally looks similar in shape whether it’s in the cells of yeast, algae, plants, or animals. But researchers have found that Euglena gracilis, a type of single-celled freshwater organism, has an unusual ATP synthase structure, according to a paper published in eLife on November 18.

Using cryo-electron microscopy, Alexey Amunts, a molecular biologist at Stockholm University in Sweden, and colleagues created a high-resolution reconstruction of the ATP synthase structure of E. gracilis. The shape and size of ATP synthase in E. gracilis is “fundamentally different” from other organisms, the authors write in their report. For example, the enzyme is larger than those found in yeast, and 13 of its 29 subunits are only found in the Euglenaceae family. Some of these distinctive parts are held together by fatty molecules called cardiolipins, which—together with the enzyme’s larger size—appear to create a curve in the mitochondrial membrane that helps ATP synthase make energy more efficiently, according to the authors.

The team’s analysis also showed structural similarities between the ATP synthases of E. gracilis and related protozoans that cause sleeping sickness and Chagas disease in humans. Studying these structures can help scientists better understand how parasites make energy.

A model of E. gracilis ATP synthase with closeup of cardiolipins (red)

A. Mühleip et al., “Structure of a mitochondrial ATP synthase with bound native cardiolipin,” eLife, doi:10.7554/eLife.51179, 2019.

Emily Makowski is an intern at The Scientist. Email her at