2. Academic Validation
  3. The hexameric structure of the human mitochondrial replicative helicase Twinkle

The hexameric structure of the human mitochondrial replicative helicase Twinkle

  • Nucleic Acids Res. 2015 Apr 30;43(8):4284-95. doi: 10.1093/nar/gkv189.
Pablo Fernández-Millán 1,  Melisa Lázaro 2,  Şirin Cansız-Arda 3,  Joachim M Gerhold 3,  Nina Rajala 4,  Claus-A Schmitz 1,  Cristina Silva-Espiña 1,  David Gil 2,  Pau Bernadó 5,  Mikel Valle 6,  Johannes N Spelbrink 7,  Maria Solà 8
Affiliations

Affiliations

  • 1 Structural MitoLab; Department of Structural Biology, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona, E-08028, Spain.
  • 2 Structural Biology Unit. Centre for Cooperative Research in Biosciences, CICbioGUNE, Derio, E-48160, Spain.
  • 3 Department of Pediatrics, Nijmegen Centre for Mitochondrial Disorders, Radboud University Medical Centre, Nijmegen, 6525 GA, The Netherlands.
  • 4 Mitochondrial DNA Maintenance Group, BioMediTech, University of Tampere, Tampere, FI-33014, Finland.
  • 5 Centre de Biochimie Structurale, INSERM-U1054, CNRS UMR-5048, Université de Montpellier I&II. Montpellier, F-34090, France.
  • 6 Structural Biology Unit. Centre for Cooperative Research in Biosciences, CICbioGUNE, Derio, E-48160, Spain mvalle@cicbiogune.es.
  • 7 Department of Pediatrics, Nijmegen Centre for Mitochondrial Disorders, Radboud University Medical Centre, Nijmegen, 6525 GA, The Netherlands Mitochondrial DNA Maintenance Group, BioMediTech, University of Tampere, Tampere, FI-33014, Finland hans.spelbrink@radboudumc.nl.
  • 8 Structural MitoLab; Department of Structural Biology, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona, E-08028, Spain maria.sola@ibmb.csic.es.
PMID: 25824949 DOI: 10.1093/nar/gkv189
Abstract

The mitochondrial replicative helicase Twinkle is involved in strand separation at the replication fork of mitochondrial DNA (mtDNA). Twinkle malfunction is associated with rare diseases that include late onset mitochondrial myopathies, neuromuscular disorders and fatal infantile mtDNA depletion syndrome. We examined its 3D structure by electron microscopy (EM) and small angle X-ray scattering (SAXS) and built the corresponding atomic models, which gave insight into the first molecular architecture of a full-length SF4 helicase that includes an N-terminal zinc-binding domain (ZBD), an intermediate RNA polymerase domain (RPD) and a RecA-like hexamerization C-terminal domain (CTD). The EM model of Twinkle reveals a hexameric two-layered ring comprising the ZBDs and RPDs in one layer and the CTDs in another. In the hexamer, contacts in trans with adjacent subunits occur between ZBDs and RPDs, and between RPDs and CTDs. The ZBDs show important structural heterogeneity. In solution, the scattering data are compatible with a mixture of extended hexa- and heptameric models in variable conformations. Overall, our structural data show a complex network of dynamic interactions that reconciles with the structural flexibility required for helicase activity.

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