Faculty Collaboration Database

Protonation state of glutamate 73 regulates the formation of a specific dimeric association of mVDAC1. Proc Natl Acad Sci U S A 2018 Jan 09;115(2):E172-E179

Date

12/28/2017

Pubmed ID

29279396

Pubmed Central ID

PMC5777057

DOI

10.1073/pnas.1715464115

Scopus ID

2-s2.0-85040219842 (requires institutional sign-in at Scopus site)   26 Citations

Abstract

The voltage-dependent anion channel (VDAC) is the most abundant protein in the outer mitochondrial membrane and constitutes the primary pathway for the exchange of ions and metabolites between the cytosol and the mitochondria. There is accumulating evidence supporting VDAC's role in mitochondrial metabolic regulation and apoptosis, where VDAC oligomerization has been implicated with these processes. Herein, we report a specific pH-dependent dimerization of murine VDAC1 (mVDAC1) identified by double electron-electron resonance and native mass spectrometry. Intermolecular distances on four singly spin-labeled mVDAC1 mutants were used to generate a model of the low-pH dimer, establishing the presence of residue E73 at the interface. This dimer arrangement is different from any oligomeric state previously described, and it forms as a steep function of pH with an apparent pK_a of 7.4. Moreover, the monomer-dimer equilibrium affinity constant was determined using native MS, revealing a nearly eightfold enhancement in dimerization affinity at low pH. Mutation of E73 to either alanine or glutamine severely reduces oligomerization, demonstrating the role of protonated E73 in enhancing dimer formation. Based on these results, and the known importance of E73 in VDAC physiology, VDAC dimerization likely plays a significant role in mitochondrial metabolic regulation and apoptosis in response to cytosolic acidification during cellular stress.

Author List

Bergdoll LA, Lerch MT, Patrick JW, Belardo K, Altenbach C, Bisignano P, Laganowsky A, Grabe M, Hubbell WL, Abramson J

Author

Michael Lerch PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Algorithms
Animals
Glutamates
Hydrogen-Ion Concentration
Kinetics
Mice
Models, Molecular
Mutation
Protein Conformation
Protein Multimerization
Protons
Voltage-Dependent Anion Channel 1