Open-Closed Structure of Light Responsive Protein LOV2 Regulates its Molecular Interaction with Binding Partner.
Abstract:
Optogenetic approaches have broad applications including regulating cell signalling and gene expression. Photo-responsive protein LOV2 and its binding partner ZDK represent an important protein caging/uncaging optogenetic system. Herein, we combine time-resolved small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) to reveal different structural states of LOV2 and the light-controlled mechanism of interaction between LOV2 and ZDK. In response to blue light within a time frame of ca. 70 s, LOV2 has a significantly higher value of radius of gyration Rg (29.6± 0.3 Å vs 26.4± 0.4 Å) than its dark state, suggesting unwinding of the C-terminal Jα-helix into an open structure. Atomic force microscopy was used to characterise molecular interactions of LOV2 in open and closed states with ZDK at a single molecule level. The closed state of LOV2 enables strong binding with ZDK, characterised by 60-fold lower dissociation rate and ~1.5 times higher activation energy barrier than its open state. In combination, these data support a light-switching mechanism that is modulated by the proximity of multiple binding sites of LOV2 for ZDK.
