The accessory helix of complexin functions by stabilizing central helix secondary structure.
The presynaptic protein complexin (CPX) is a critical regulator of synaptic vesicle fusion, but the mechanisms underlying its regulatory effects are not well understood. Its highly conserved central helix (CH) directly binds the ternary SNARE complex and is required for all known CPX functions. The adjacent accessory helix (AH) is not conserved despite also playing an important role in CPX function, and numerous models for its mechanism have been proposed. We examined the impact of AH mutations and chimeras on CPX function in vivo and in vitro usingC. elegans. The mouse AH fully restored function when substituted into worm CPX suggesting its mechanism is evolutionarily conserved. CPX inhibitory function was impaired when helix propagation into the CH was disrupted whereas replacing the AH with a non-native helical sequence restored CPX function. We propose that the AH operates by stabilizing CH secondary structure rather than through protein or lipid interactions.
Department of Biochemistry, Weill Cornell Medical College, New York, United States.
Daniel T
DT
Radoff
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.
Yongming
Y
Dong
Department of Biochemistry, Weill Cornell Medical College, New York, United States.
David
D
Snead
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.
Jihong
J
Bai
Department of Biochemistry, Weill Cornell Medical College, New York, United States.
David
D
Eliezer
Department of Biochemistry, Weill Cornell Medical College, New York, United States.
Jeremy S
JS
Dittman
C. elegans; SNARE; biophysics; complexin; exocytosis; neuroscience; structural biology; synaptic transmission