title: Conformational Flexibility Enables the Function of a BECN1 Region Essential for Starvation-Mediated Autophagy.
abstract: 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.
authors.affiliation: Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Mei
authors.affiliation: Health Data Sciences Institute, Computational Science and Engineering Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37830, United States.
authors.forename: Arvind
authors.initials: A
authors.lastname: Ramanathan
authors.affiliation: Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.
authors.forename: Karen
authors.initials: K
authors.lastname: Glover
authors.affiliation: Biology and Soft Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Christopher
authors.initials: C
authors.lastname: Stanley
authors.affiliation: GMCA@APS, X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Ruslan
authors.initials: R
authors.lastname: Sanishvili
authors.affiliation: Bio-CAT, Advanced Photon Source , 9700 South Cass Avenue, Building 435B, Argonne, Illinois 60439, United States.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Chakravarthy
authors.affiliation: Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.
authors.forename: Zhongyu
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Colbert
authors.affiliation: Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.
authors.forename: Sangita C
authors.initials: SC
authors.lastname: Sinha
mesh_terms: D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001343:Autophagy; D000071186:Beclin-1; D015415:Biomarkers / Q000378:metabolism; D045744:Cell Line, Tumor; D017124:Conserved Sequence; D016895:Culture Media, Serum-Free; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018583:Pliability; D017354:Point Mutation; D011487:Protein Conformation; D058849:Protein Refolding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D015415:Biomarkers; D016895:Culture Media, Serum-Free; D008565:Membrane Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins