GCaMP is one of the most widely used calcium indicators in neuronal imaging and calcium cell biology. The newly developed GCaMP6 shows superior brightness and ultrasensitivity to calcium concentration change. In this study, we determined crystal structures of CaZ＋-bound GCaMP6 monomer and dimer and presented detailed structural analyses in comparison with its par- ent version GCaMP5G. Our analyses reveal the structural basis for the outperformance of this newly developed Ca2＋ indicator. Three substitution mutations and the resulting changes of local structure and interaction explain the ultrasensitivity and in- creased fluorescence intensity common to all three versions of GCaMP6. Each particular substitution in the three GCaMP6 is also structurally consistent with their differential sensitivity and intensity, maximizing the potential of using GCaMP6 in solving diverse problems in neuronal research and calcium signaling. Our studies shall also be beneficial to further structure-guided optimization of GCaMP and facilitate the design of novel calcium indicators.
DING JingJinLUO Andrew F.HU LiYanWANG DaChengSHAO Feng
In this review we summarize the progress made towards understanding the role of protein-protein interactions in the function of various bioluminescence systems of marine organisms,including bacteria,jellyfish and soft corals,with particular focus on methodology used to detect and characterize these interactions.In some bioluminescence systems,protein-protein interactions involve an“accessory protein”whereby a stored substrate is efficiently delivered to the bioluminescent enzyme luciferase.Other types of complexation mediate energy transfer to an“antenna protein”altering the color and quantum yield of a bioluminescence reaction.Spatial structures of the complexes reveal an important role of electrostatic forces in governing the corresponding weak interactions and define the nature of the interaction surfaces.The most reliable structural model is available for the protein-protein complex of the Ca2+-regulated photoprotein clytin and green-fluorescent protein(GFP)from the jellyfish Clytia gregaria,solved by means of Xray crystallography,NMR mapping and molecular docking.This provides an example of the potential strategies in studying the transient complexes involved in bioluminescence.It is emphasized that structural studies such as these can provide valuable insight into the detailed mechanism of bioluminescence.
Maxim S.TitushinYingang FengJohn LeeEugene S.VysotskiZhi-Jie Liu
