Unique Structural Features of the Mitochondrial AAA+ Protease AFG3L2 Reveal the Molecular Basis for Activity in Health and Disease

Mol Cell. 2019 Sep 5;75(5):1073-1085.e6. doi: 10.1016/j.molcel.2019.06.016. Epub 2019 Jul 18.


Mitochondrial AAA+ quality-control proteases regulate diverse aspects of mitochondrial biology through specialized protein degradation, but the underlying mechanisms of these enzymes remain poorly defined. The mitochondrial AAA+ protease AFG3L2 is of particular interest, as genetic mutations localized throughout AFG3L2 are linked to diverse neurodegenerative disorders. However, a lack of structural data has limited our understanding of how mutations impact enzymatic function. Here, we used cryoelectron microscopy (cryo-EM) to determine a substrate-bound structure of the catalytic core of human AFG3L2. This structure identifies multiple specialized structural features that integrate with conserved motifs required for ATP-dependent translocation to unfold and degrade targeted proteins. Many disease-relevant mutations localize to these unique structural features of AFG3L2 and distinctly influence its activity and stability. Our results provide a molecular basis for neurological phenotypes associated with different AFG3L2 mutations and establish a structural framework to understand how different members of the AAA+ superfamily achieve specialized biological functions.

Keywords: AAA+ protease; mitochondrial quality control; neurodegenerative disease; spinocerebellar ataxia type 28.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • ATP-Dependent Proteases / chemistry*
  • ATP-Dependent Proteases / genetics
  • ATP-Dependent Proteases / metabolism
  • ATPases Associated with Diverse Cellular Activities / chemistry*
  • ATPases Associated with Diverse Cellular Activities / genetics
  • ATPases Associated with Diverse Cellular Activities / metabolism
  • Cryoelectron Microscopy
  • HEK293 Cells
  • Heredodegenerative Disorders, Nervous System / genetics
  • Heredodegenerative Disorders, Nervous System / metabolism
  • Humans
  • Mitochondrial Proteins / chemistry*
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Mutation*
  • Protein Domains


  • Mitochondrial Proteins
  • ATP-Dependent Proteases
  • AFG3L2 protein, human
  • ATPases Associated with Diverse Cellular Activities