Folded Structure and Membrane Affinity of the N‑Terminal Domain of the Three Human Isoforms of the Mitochondrial Voltage-Dependent Anion-Selective Channel
journal contributionposted on 19.09.2018, 16:49 by Giorgia Manzo, Ilaria Serra, Andrea Magrí, Mariano Casu, Vito De Pinto, Matteo Ceccarelli, Mariano Andrea Scorciapino
Voltage-dependent anion-selective channels (VDACs) are primarily located in the mitochondrial outer membrane (MOM). They are essential for the regulation of ion and metabolite exchanges. In particular, their role in energy-related nucleotide exchange has many implications in apoptosis, cancer, and neurodegenerative diseases. It has been proposed that VDACs’ functions are regulated by mobility of the N-terminal helical domain, which is bound to the inner wall of the main β-barrel domain but exists in equilibrium between the bound-folded and the unbound-unfolded state. When the N-terminal domain detaches from the channel’s wall and eventually leaves the lumen, it can either stay exposed to the cytosolic environment or interact with the outer leaflet of the MOM; then, it may also interact with other protein partners. In humans, three different VDAC isoforms are expressed at different tissue-specific levels with evidence of distinct roles. Although the N-terminal domains share high sequence similarity, important differences do exist, with the functionality of the entire protein mostly attributed to them. In this work, the three-dimensional structure and membrane affinity of the three isolated hVDAC N-terminal peptides have been compared through Fourier-transform infrared and NMR spectroscopy in combination with molecular dynamics simulations, and measurement of the surface pressure of lipid monolayers. Although peptides were studied as isolated from the β-barrel domain, the observed differences are relevant for those whole protein’s functions in which a protein–protein interaction is mediated by the N-terminal domain.
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β- barrel domainmembrane affinityN-terminal domain detachesN-terminal domainunbound-unfolded stateMitochondrial Voltage-Dependent Anion-Selective Channel Voltage-dependent anion-selective channelsmetabolite exchangessurface pressurehVDAC N-terminal peptidesFolded StructureMembrane Affinityneurodegenerative diseasesprotein partnersN-terminal helical domainsequence similaritycytosolic environmentHuman IsoformsNMR spectroscopyenergy-related nucleotide exchangetissue-specific levelsVDAC isoformslipid monolayersdynamics simulationsN-terminal domains share