Heat-induced dimerization of BCL-xL through alpha-helix swapping.
The dimerization of anti-apoptotic BCL-xL by three-dimensional domain swapping has recently been discovered at alkaline pH; however, the high energetic barrier between the dimer and monomer forms of BCL-xL prevents them from interconverting at room temperature and neutral pH. Here, we demonstrate that BCL-xL dimers can be easily prepared by heating concentrated protein above 50 degrees C. The 38 kDa BCL-xL dimer was fully characterized by multi-resonance nuclear magnetic resonance (NMR) spectroscopy, and the mechanism of dimerization by alpha-helix swapping was confirmed. Dimerization strongly affects the NMR signals from the turn between helices alpha5 and alpha6 of BCL-xL and a portion of the long loop between helices alpha1 and alpha2. Measurements of residual dipolar couplings demonstrate that the solution structure of the BCL-xL dimer is very close to the crystal structure. Dimer formation does not prevent tight binding of ligands to the hydrophobic cleft of BCL-xL; however, binding of a BID BH3-peptide or a polyphenol drug, gossypol, to BCL-xL significantly slowed monomer-dimer interconversion and is an example of the control of BCL protein oligomerization by ligand binding.
Denisov
Alexey Yu
AY
Department of Biochemistry, McGill University, Montreal, Québec H3G 1Y6, Canada.
Sprules
Tara
T
Fraser
James
J
Kozlov
Guennadi
G
Gehring
Kalle
K
D000818:Animals; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D001665:Binding Sites; D003460:Crystallization; D019281:Dimerization; D006072:Gossypol / Q000737:chemistry / Q000378:metabolism; D006358:Hot Temperature; D051379:Mice; D019906:Nuclear Magnetic Resonance, Biomolecular; D051020:bcl-X Protein / Q000737:chemistry* / Q000378:metabolism
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C494812:Bcl2l1 protein, mouse; D051020:bcl-X Protein; D006072:Gossypol