Biology subjects

Yu, C. W. H.

Publications and source records attributed to Yu, C. W. H..

2 recordsLinked to original sources

bioRxiv2024

Molecular mechanism of Mad2 conformational conversion promoted by the Mad2-interaction motif of Cdc20

During mitosis, unattached kinetochores trigger the spindle assembly checkpoint by promoting assembly of the mitotic checkpoint complex, a heterotetramer comprising Mad2, Cdc20, BubR1 and Bub3. Critical to this process is the kinetochore-mediated catalysis of an intrinsically slow conformational conversion of Mad2 from an open (O-Mad2) inactive state to a closed (C-Mad2) active state bound to Cdc20. These Mad2 conformational changes involve substantial remodelling of the N-terminal {beta}1 strand and C-terminal {beta}7/{beta}8 hairpin. In vitro, the Mad2- interaction motif (MIM) of Cdc20 (Cdc20MIM) triggers rapid conversion of O- to C-Mad2, effectively removing the kinetic barrier for MCC assembly. How Cdc20MIM directly induces Mad2 conversion remains unclear. In this study we demonstrate that the Cdc20MIM-binding site is inaccessible in O-Mad2. Time-resolved NMR and molecular dynamics simulations show how Mad2 conversion involves sequential conformational changes of flexible structural elements in O-Mad2, orchestrated by Cdc20MIM. Conversion is initiated by the {beta}7/{beta}8 hairpin of O-Mad2 transiently unfolding to expose a nascent Cdc20MIM-binding site. Engagement of Cdc20MIM to this site promotes release of the {beta}1 strand. We propose that initial conformational changes of the {beta}7/{beta}8 hairpin allows binding of Cdc20MIM to a transient intermediate state of Mad2, thereby lowering the kinetic barrier to Mad2 conversion.

biochemistry↗

bioRxiv2022

A molecular mechanism for membrane chaperoning by a late embryogenesis abundant protein

Environmental stress can result in substantial damage to proteins, membranes, and genetic material, impacting organismal survival1-3. Stress tolerance can be conferred by intrinsically disordered proteins (IDPs)4 that lack stable tertiary structure. IDPs from the large family of late embryogenesis abundant (LEA) proteins confer a fitness advantage when heterologously expressed5,6. Such protection suggests a general molecular function leading to stress tolerance, although the mechanisms remain unclear. Here, we report that a tardigrade LEA protein that confers stress tolerance in yeast acts as a molecular chaperone for the mitochondrial membrane. This protein, named HeLEA1, localizes to the mitochondrial matrix, and harbors conserved LEA sequence motifs that undergo dynamic disorder-to-helical transition upon binding to negatively charged membranes. Yeast expressing HeLEA1 show increased mitochondrial membrane fluidity, increased membrane potential, and enhanced tolerance to hyperosmotic stress under non-fermentative growth without significantly altering mitochondrial lipid composition or triggering a generic stress response. We demonstrate that membrane binding ameliorates excess surface tension, possibly by stabilizing lipid packing defects. Evolutionary analysis suggests that HeLEA1 homologs localize to different membrane-bound organelles and share similar sequence and biophysical features. We suggest that membrane chaperoning by LEA proteins represents a general biophysical solution that can operate across the domains of life.

biophysics↗