The hexameric structure of the human mitochondrial replicative helicase Twinkle

Area of Science:

• Biochemistry
• Structural Biology
• Genetics

Background:

• Mitochondrial DNA (mtDNA) replication relies on the replicative helicase Twinkle.
• Twinkle dysfunction is linked to severe genetic disorders, including mtDNA depletion syndrome and mitochondrial myopathies.

Purpose of the Study:

• To elucidate the molecular architecture of the full-length mitochondrial replicative helicase Twinkle.
• To understand the structural basis of Twinkle's function and its role in disease.

Main Methods:

• 3D structure determination using electron microscopy (EM).
• Small-angle X-ray scattering (SAXS) for solution-based structural analysis.
• Atomic model building of the Twinkle helicase.

Main Results:

• Revealed the first atomic model of a full-length SF4 helicase, comprising N-terminal zinc-binding (ZBD), RNA polymerase (RPD), and C-terminal RecA-like hexamerization (CTD) domains.
• EM data showed a two-layered hexameric ring structure with specific inter-domain contacts.
• SAXS data indicated conformational flexibility and potential hexa- and heptameric forms in solution.

Conclusions:

• The structure of Twinkle displays a dynamic network of interactions essential for its helicase activity.
• Understanding Twinkle's structure provides insights into the mechanisms underlying mtDNA replication and associated diseases.