Method for the structural analysis of Twinkle mitochondrial DNA helicase by cryo-EM

The mitochondrial replisome replicates the 16.6 kb mitochondria DNA (mtDNA). The proper functioning of this multicomponent protein complex is vital for the integrity of the mitochondrial genome. One of the critical protein components of the mitochondrial replisome is the Twinkle helicase, a member of the Superfamily 4 (SF4) helicases. Decades of research has uncovered common themes among SF4 helicases including self-assembly, ATP-dependent translocation, and formation of protein-protein complexes. Some of the molecular details of these processes are still unknown for the mitochondria SF4 helicase, Twinkle. Here, we describe a protocol for expression, purification, and single-particle cryo-electron microscopy of the Twinkle helicase clinical variant, W315L, which resulted in the first high-resolution structure of Twinkle helicase. The methods described here serve as an adaptable protocol to support future high-resolution studies of Twinkle helicase or other SF4 helicases.

Automated summary

The mitochondrial replisome is crucial for replicating mtDNA, with Twinkle helicase being a key protein component. Studying SF4 helicases helps understand common themes like self-assembly, ATP-dependent translocation, and formation of protein complexes. The methods described can support future high-resolution studies of Twinkle helicase or other SF4 helicases.