Student Posters 51st Lorne Proteins Conference 2026

A Twist in the Tail: The Structural Basis of Kv7.2/Kv7.3 M-channel Assembly at Helix D (#142)

MariaKatarina Lambourne 1 2 , Tom Peat 3 , Gökhan Tolun 1 2 , Aidan Grosas 1 2 , Lezanne Ooi 1 2
  1. School of Science and Molecular Horizons Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
  2. ARC Industrial Transformation Training Centre for Cryo-electron Microscopy of Membrane Proteins, University of Wollongong, Wollongong, NSW 2522, Australia
  3. School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia

Epilepsy is one of the most prevalent neurological disorders, affecting approximately 65 million people worldwide1. It is characterised by recurrent seizures, the severity of which can be influenced by genetic, environmental, or unknown factors. One in three individuals with epilepsy do not respond to current treatments2, highlighting the need for better mechanistic understanding to develop more effective therapies.

The Kv7 family of voltage-gated potassium channels (Kv7.1–Kv7.5), encoded by KCNQ genes, has been implicated in epilepsy3. Kv7.2 and Kv7.3 form a majority of the neuronal M-channel, which regulates neuronal excitability by generating the stabilising M-current that prevents excessive firing. Mutations in the KCNQ genes, particularly within the transmembrane and regulatory domains of Kv7.2 and Kv7.3, are strongly associated with epilepsy.

A novel mutation has been identified in Kv7.3 within the proposed assembly domain, Helix D, resulting from a glutamine to leucine substitution (Q653L). Its effects on channel function remain unknown but may reveal a new mechanism. Additionally, Helix D has eluded structural studies of full-length Kv7 channels due to its location at the end of the highly flexible cytoplasmic C-terminal tail. On a domain level, crystal structures of Helix D from Kv7.1 and Kv7.4 reveal strong tetramer networks contributing to channel assembly4,5. However, size-exclusion chromatography of this isolated region shows Kv7.3 favours monomeric and homodimeric states4. Given that Helix D in Kv7.3 has a lower sequence conservation within the Kv7 family and plays a key role in heteromeric assembly, further investigation is needed to clarify its contribution to M-channel formation.

Here, we present the first crystal structures of Kv7.2 Helix D and a heteromeric Kv7.2/Kv7.3 Helix D complex, revealing key interfaces that likely mediate subunit association. Complementary biophysical analyses, including size-exclusion chromatography, multi-angle light scattering, mass photometry, and circular dichroism spectroscopy, show that Helix D forms a dynamic assembly capable of supporting distinct oligomeric states. These findings provide a framework for understanding Kv7 channel assembly and lay a strong foundation for ongoing cryo-EM studies of Kv7.2/Kv7.3 channels.

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  2. Chen Z, Brodie MJ, Liew D, Kwan P. Treatment Outcomes in Patients With Newly Diagnosed Epilepsy Treated With Established and New Antiepileptic Drugs: A 30-Year Longitudinal Cohort Study. JAMA Neurol. 2018.
  3. Nappi P, Miceli F, Soldovieri MV, Ambrosino P, Barrese V, Taglialatela M. Epileptic channelopathies caused by neuronal Kv7 (KCNQ) channel dysfunction. Pflüg Arch - Eur J Physiol. 2020.
  4. Howard RJ, Clark KA, Holton JM, Minor DL. Structural insight into KCNQ (Kv7) channel assembly and channelopathy. Neuron. 2007.
  5. Wiener R, Haitin Y, Shamgar L, et al. The KCNQ1 (Kv7.1) COOH Terminus, a Multitiered Scaffold for Subunit Assembly and Protein Interaction. J Biol Chem. 2008.