5HJQ

Crystal structure of the TBC domain of Skywalker/TBC1D24 from Drosophila melanogaster in complex with inositol(1,4,5)triphosphate

Summary for 5HJQ

• Entry DOI: 10.2210/pdb5hjq/pdb
• Descriptor: LD10117p, D-MYO-INOSITOL-1,4,5-TRIPHOSPHATE (3 entities in total)
• Functional Keywords: tbc, rabgap, signaling protein
• Biological source: Drosophila melanogaster (Fruit fly)
• Total number of polymer chains: 1
• Total formula weight: 43516.89

Authors

Fischer, B.,Paesmans, J.,Versees, W. (deposition date: 2016-01-13, release date: 2016-09-21, Last modification date: 2024-01-10)

Primary citation

Fischer, B.,Luthy, K.,Paesmans, J.,De Koninck, C.,Maes, I.,Swerts, J.,Kuenen, S.,Uytterhoeven, V.,Verstreken, P.,Versees, W.
Skywalker-TBC1D24 has a lipid-binding pocket mutated in epilepsy and required for synaptic function.
Nat.Struct.Mol.Biol., 23:965-973, 2016

PubMed Abstract: Mutations in TBC1D24 cause severe epilepsy and DOORS syndrome, but the molecular mechanisms underlying these pathologies are unresolved. We solved the crystal structure of the TBC domain of the Drosophila ortholog Skywalker, revealing an unanticipated cationic pocket conserved among TBC1D24 homologs. Cocrystallization and biochemistry showed that this pocket binds phosphoinositides phosphorylated at the 4 and 5 positions. The most prevalent patient mutations affect the phosphoinositide-binding pocket and inhibit lipid binding. Using in vivo photobleaching of Skywalker-GFP mutants, including pathogenic mutants, we showed that membrane binding via this pocket restricts Skywalker diffusion in presynaptic terminals. Additionally, the pathogenic mutations cause severe neurological defects in flies, including impaired synaptic-vesicle trafficking and seizures, and these defects are reversed by genetically increasing synaptic PI(4,5)P concentrations through synaptojanin mutations. Hence, we discovered that a TBC domain affected by clinical mutations directly binds phosphoinositides through a cationic pocket and that phosphoinositide binding is critical for presynaptic function.

PubMed: 27669036
DOI: 10.1038/nsmb.3297

Experimental method

X-RAY DIFFRACTION (2.3 Å)