Characterization of the Full-Length, Human Beclin-1 Purified from Escherichia Coli

We report here the first synthesis and functional characterization of the full-length, human homolog of Beclin-1 that was generated as a recombinant protein from Escherichia coli. Beclin-1 is essential for initiating macroautophagy (herein called autophagy); a highly conserved survival mechanism that recycles damaged cellular components (e.g., proteins, organelles) or pathogens by encasing them in a bilayer vesicle (termed autophagosome) that fuses with a lysosome to enable degradation of the vesicular contents. Mutations in or altered expression profiles of Beclin-1 are well documented to be involved in various cancers and neurodegenerative diseases. Moreover, several viruses (including HIV and HSV-1) specifically target Beclin-1 as a means to evade host defense mechanisms. We demonstrate that our recombinant Beclin-1 protein exists as a soluble homodimeric species in solution, undergoes reversible monomer-dimer equilibrium, binds lipid membranes, and interacts with HIV Nef and the anti-apoptotic Bcl-2 proteins.