Biology subjects

Glynn, S. E.

Publications and source records attributed to Glynn, S. E..

3 recordsLinked to original sources

bioRxiv2025

Recognition of small Tim chaperones by the mitochondrial Yme1 protease

Yme1 is a conserved ATP-dependent protease that maintains mitochondrial function by degrading proteins in the intermembrane space. However, how Yme1 selects substrates within the crowded mitochondrial environment is poorly understood. An established substrate of Yme1 in yeast is the Tim10 subunit of the small Tim9-Tim10 protein chaperone complex, which is degraded following disruption of the subunits internal disulfide bonds. Here, we use biochemical and biophysical approaches to examine initial substrate binding and degradation of small Tim proteins by Yme1 and shed light on the molecular mechanism of substrate selection. We show that Yme1 preferentially binds Tim10 over other small Tim proteins by forming a high-affinity interaction with the subunit irrespective of the presence of its disulfide bonds. This interaction is primarily mediated by Tim10s flexible N-terminal tentacle, though substrate unfolding exposes additional contact sites that enhance engagement. Notably, the human ortholog TIMM13 is also recognized by yeast Yme1, suggesting conservation of recognition strategy across species. Yme1 also binds to the assembled Tim9-Tim10 chaperone but independently of the Tim10 N-terminal tentacle. These findings suggest that Yme1 surveils the folding state of Tim10 throughout its functional lifecycle - both as a folded monomer and as a subunit of the functional chaperone complex - but only commits to degradation after disruption of its disulfide bonds.

biochemistry↗

bioRxiv2019

Unique structural features of the mitochondrial AAA+ protease AFG3L2 reveal the molecular basis for activity in health and disease

Mitochondrial AAA+ quality control proteases regulate diverse aspects of mitochondrial biology through specialized protein degradation, but the underlying molecular mechanisms that define the diverse activities 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 activity. Here, we used cryo-EM to determine a substrate-bound structure of the catalytic core of human AFG3L2. This structure identifies multiple specialized structural features within AFG3L2 that integrate with conserved structural motifs required for hand-over-hand ATP-dependent substrate translocation to engage, unfold and degrade targeted proteins. Mapping disease-relevant AFG3L2 mutations onto our structure demonstrates that many of these 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, diverse biological functions.

molecular biology↗

bioRxiv2017

Atomic structure of the mitochondrial inner membrane AAA+ protease YME1 reveals the mechanism of substrate processing

We present the first atomic model of a substrate-bound inner mitochondrial membrane AAA+ quality control protease, YME1. Our ~3.4 [A] cryo-EM structure reveals how the ATPases form a closed spiral staircase encircling an unfolded substrate, directing it toward the flat, symmetric protease ring. Importantly, the structure reveals how three coexisting nucleotide states allosterically induce distinct positioning of tyrosines in the central channel, resulting in substrate engagement and translocation to the negatively charged proteolytic chamber. This tight coordination by a network of conserved residues defines a sequential, around-the-ring ATP hydrolysis cycle that results in step-wise substrate translocation. Furthermore, we identify a hinge-like linker that accommodates the large-scale nucleotide-driven motions of the ATPase spiral independently of the contiguous planar proteolytic base. These results define the first molecular mechanism for a mitochondrial inner membrane AAA+ protease and reveal a translocation mechanism likely conserved for other AAA+ ATPases.

molecular biology↗