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Publication Abstract from PubMed

Permeabilization of the outer mitochondrial membrane by pore-forming Bcl2 proteins is a crucial step for the induction of apoptosis. Despite a large set of data suggesting global conformational changes within pro-apoptotic Bak during pore formation, high-resolution structural details in a membrane environment remain sparse. Here, we used NMR and HDX-MS (Hydrogen deuterium exchange mass spectrometry) in lipid nanodiscs to gain important high-resolution structural insights into the conformational changes of Bak at the membrane that are dependent on a direct activation by BH3-only proteins. Furthermore, we determined the first high-resolution structure of the Bak transmembrane helix. Upon activation, alpha-helix 1 in the soluble domain of Bak dissociates from the protein and adopts an unfolded and dynamic potentially membrane-bound state. In line with this finding, comparative protein folding experiments with Bak and anti-apoptotic BclxL suggest that alpha-helix 1 in Bak is a metastable structural element contributing to its pro-apoptotic features. Consequently, mutagenesis experiments aimed at stabilizing alpha-helix 1 yielded Bak variants with delayed pore-forming activity. These insights will contribute to a better mechanistic understanding of Bak-mediated membrane permeabilization.

High-resolution analysis of the conformational transition of pro-apoptotic Bak at the lipid membrane.,Sperl LE, Ruhrnossl F, Schiller A, Haslbeck M, Hagn F EMBO J. 2021 Oct 18;40(20):e107159. doi: 10.15252/embj.2020107159. Epub 2021 Sep , 15. PMID:34523144^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.