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Biochemistry DOI:10.1021/acs.biochem.7b00936

The Autophagy-Related Beclin-1 Protein Requires the Coiled-Coil and BARA Domains To Form a Homodimer with Submicromolar Affinity.

Publication TypeJournal Article
Year of Publication2017
AuthorsRanaghan, MJ, Durney, MA, Mesleh, MF, McCarren, PR, Garvie, CW, Daniels, DS, Carey, KL, Skepner, AP, Levine, B, Perez, JR
Date Published2017 12 26
KeywordsAmino Acid Sequence, Autophagy, Beclin-1, Escherichia coli, Humans, Mutagenesis, Site-Directed, Protein Domains, Protein Multimerization, Protein Structure, Secondary, Recombinant Proteins

Beclin-1 (BECN1) is an essential component of macroautophagy. This process is a highly conserved survival mechanism that recycles damaged cellular components or pathogens by encasing them in a bilayer vesicle that fuses with a lysosome to allow degradation of the vesicular contents. Mutations or altered expression profiles of BECN1 have been linked to various cancers and neurodegenerative diseases. Viruses, including HIV and herpes simplex virus 1 (HSV-1), are also known to specifically target BECN1 as a means of evading host defense mechanisms. Autophagy is regulated by the interaction between BECN1 and Bcl-2, a pro-survival protein in the apoptotic pathway that stabilizes the BECN1 homodimer. Disruption of the homodimer by phosphorylation or competitive binding promotes autophagy through an unknown mechanism. We report here the first recombinant synthesis (3-5 mg/L in an Escherichia coli culture) and characterization of full-length, human BECN1. Our analysis reveals that full-length BECN1 exists as a soluble homodimer (K ∼ 0.45 μM) that interacts with Bcl-2 (K = 4.3 ± 1.2 μM) and binds to lipid membranes. Dimerization is proposed to be mediated by a coiled-coil region of BECN1. A construct lacking the C-terminal BARA domain but including the coiled-coil region exhibits a homodimer K 3.5-fold weaker than that of full-length BECN1, indicating that both the BARA domain and the coiled-coil region of BECN1 contribute to dimer formation. Using site-directed mutagenesis, we show that residues at the C-terminus of the coiled-coil region previously shown to interact with the BARA domain play a key role in dimerization and mutations weaken the interface by ∼5-fold.


Alternate JournalBiochemistry
PubMed ID29185708
PubMed Central IDPMC5842915
Grant ListU19 AI109725 / AI / NIAID NIH HHS / United States