Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
SHR Neuro Krebs Kardio Lipid Stoffw Microb
Rawal, S; Kolarić, Ð; Bohn, S; Kolb, D; Pavkov-Keller, T; Pritišanac, I; Madl, T; Desfosses, A; Reid, Alderson, T.
A histidine switch regulates pH-dependent filament formation by the caspase-9 CARD.
bioRxiv. 2025;
Doi: 10.1101/2025.06.02.657148
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PubMed
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- Autor*innen der Med Uni Graz:
- Alderson Thomas Reid
- Kolb Dagmar
- Madl Tobias
- Pritisanac Iva
- Rawal Swasti
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- Abstract:
- The caspase activation and recruitment domain (CARD) mediates protein-protein interactions in apoptotic and inflammatory signaling pathways. In humans, more than 30 proteins contain a CARD, several of which have been reported to polymerize into helical filaments. Here we found that the CARD from the apoptotic protease caspase-9 (C9CARD) self assembles into filaments in vitro at physiological pH and salt concentrations. The C9CARD more readily polymerizes under low-salt or mildly acidic conditions, suggesting a significant role for electrostatic interactions in mediating filament formation. Using NMR spectroscopy, we determined the pK a of the lone histidine residue, H38, which supports a role for histidine protonation in enhancing filament formation. Indeed, mutation of H38 to introduce a positive (H38R) or negative (H38D) charge, or to remove the pH-dependence of the side chain at this site altogether (H38N), dramatically alters the filament propensity of the domain. Using cryo-election microscopy, we determined 3.4- and 3.2-Å structures of the wild-type and H38R C9CARD filaments, respectively, which provide new insights into the molecular basis of C9CARD polymerization and its pH dependence via H38.