Open AccessConformational Flexibility Enables the Function of a BECN1 Region Essential for Starvation-Mediated Autophagy
Author(s) -
Mei Yang,
Arvind Ramanathan,
Karen Glover,
Christopher B. Stanley,
Ruslan Sanishvili,
Srinivas Chakravarthy,
Zhongyu Yang,
Christopher L. Colbert,
Sangita C. Sinha
Publication year - 2016
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/acs.biochem.5b01264
Subject(s) - circular dichroism , becn1 , crystallography , autophagy , chemistry , helix (gastropod) , coiled coil , context (archaeology) , small angle x ray scattering , biophysics , protein structure , biochemistry , biology , scattering , physics , apoptosis , ecology , paleontology , snail , optics
BECN1 is essential for autophagy, a critical eukaryotic cellular homeostasis pathway. Here we delineate a highly conserved BECN1 domain located between previously characterized BH3 and coiled-coil domains and elucidate its structure and role in autophagy. The 2.0 Å sulfur-single-wavelength anomalous dispersion X-ray crystal structure of this domain demonstrates that its N-terminal half is unstructured while its C-terminal half is helical; hence, we name it the flexible helical domain (FHD). Circular dichroism spectroscopy, double electron-electron resonance-electron paramagnetic resonance, and small-angle X-ray scattering (SAXS) analyses confirm that the FHD is partially disordered, even in the context of adjacent BECN1 domains. Molecular dynamic simulations fitted to SAXS data indicate that the FHD transiently samples more helical conformations. FHD helicity increases in 2,2,2-trifluoroethanol, suggesting it may become more helical upon binding. Lastly, cellular studies show that conserved FHD residues are required for starvation-induced autophagy. Thus, the FHD likely undergoes a binding-associated disorder-to-helix transition, and conserved residues critical for this interaction are essential for starvation-induced autophagy.