Biology subjects

Ault, J. R.

Publications and source records attributed to Ault, J. R..

3 recordsLinked to original sources

bioRxiv2023

Cryo-EM structure of the CDK2-cyclin A-CDC25A complex

The cell division cycle 25 phosphatases CDC25A, B and C regulate cell cycle transitions by dephosphorylating residues in the conserved glycine-rich motif of cyclin-dependent protein kinases (CDKs) to activate CDK activity. Here, we present the cryogenic-electron microscopy (cryo-EM) structure of CDK2-cyclin A in complex with CDC25A at 2.91 [A] resolution, providing a detailed structural analysis of the overall complex architecture and key protein-protein interactions that underpin this 86 kDa complex. We further reveal an unanticipated CDC25A C-terminal helix that is critical for complex formation. Sequence conservation analysis suggests CDK1/2-cyclin A, CDK1-cyclin B and CDK2/3-cyclin E are suitable binding partners for CDC25A, whilst CDK4/6-cyclin D complexes appear unlikely substrates. A comparative structural analysis of CDK-containing complexes also confirms the functional importance of the conserved CDK1/2 GDSEID motif. This structure improves our understanding of the roles of CDC25 phosphatases in CDK regulation and may inform the development of CDC25- targeting anticancer strategies.

biochemistry↗

bioRxiv2021

Mechanical and molecular activation lead to structurally analogous MscL states

The MscL channel gates in response to membrane tension changes to allow the exchange of molecules through its pore. Lipid removal from transmembrane pockets leads to a MscL response. However, it is unknown whether there is correlation between the tension mediated state and the state derived by pocket delipidation in the absence of tension. Transitions between MscL states may follow a similar pathway to cover the available conformational space but may not necessarily sample the same discrete intermediates. Here, we combined pulsed-EPR and HDX-MS measurements on MscL, coupled with molecular dynamics under membrane tension, to investigate the changes associated with the distinctively derived states. Whether it is tension or pocket delipidation, we find that MscL samples a similar expanded state, which is the final step of the delipidation pathway but only an intermediate stop of the tension mediated path. Our findings hint at synergistic modes of regulation in mechanosensitive channels.

biophysics↗

bioRxiv2020

Discriminative SKP2 interactions with CDK-cyclin complexes support a cyclin A-specific role in p27KIP1 degradation

The SCFSKP2 ubiquitin ligase relieves G1 checkpoint control of CDK-cyclin complexes by promoting p27KIP1 degradation. We describe reconstitution of stable complexes containing SKP1-SKP2 and CDK1-cyclin B or CDK2-cyclin A/E, mediated by the CDK regulatory subunit CKS1. We further show that a direct interaction between a SKP2 N-terminal motif and cyclin A can stabilize SKP1-SKP2-CDK2-cyclin A complexes in the absence of CKS1. We identify the SKP2 binding site on cyclin A and demonstrate the site is not present in cyclin B or cyclin E. This site is distinct from but overlapping with features that mediate binding of p27KIP1 and other G1 cyclin regulators to cyclin A. We propose that the capacity of SKP2 to engage with CDK2-cyclin A by more than one structural mechanism provides a way to fine tune the degradation of p27KIP1 and distinguishes cyclin A from other G1 cyclins to ensure orderly cell cycle progression.

biochemistry↗