Abstract
Mical1 regulates F-actin dynamics through the reversible oxidation of actin, a process controlled by its interactions with various proteins. Upon binding to Rab8 family members, Mical1 links endosomes to the cytoskeleton, promoting F-actin disassembly. In the absence of Rab, Mical1 exists in an auto-inhibited state, but its biochemical characterization remains incomplete. Our study reveals that the N-terminal MO-CH-LIM domains of Mical1 form an intramolecular complex with its C-terminal bMERB domain. Mutational analysis, guided by the AlphaFold2 model, identifies critical residues at the binding interface. Additionally, we demonstrate that full-length Mical1 binds to Rab8 in a 1:2 stoichiometry, thereby releasing auto-inhibition. Through structure-based mutational studies, we uncover allostery between the N and C-terminal Rab binding sites. Notably, Rab binding at the high-affinity C-terminal site precedes binding at the N-terminal site, suggesting a sequential binding mode. These findings elucidate how Rab8 binding releases the MO-CH-LIM domains from the Mical1 bMERB domain, facilitating interactions with other proteins and the actin cytoskeleton, thereby modulating actin dynamics.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Open access funding statement is included in the revised manuscript
