The interactions between B-cell lymphoma 2 (BCL-2) family members are known to be mediated through the binding of the BH3 domain of a proapoptotic member to the BH3-binding groove of an antiapoptotic member. We determined the crystal structure of antiapoptotic CED-9, which reveals a unique C-terminal helix altering the common BH3-binding region. A coexpression system to produce CED-9 in complex with proapoptotic EGL-1 enabled us to show that the binding of EGL-1 to CED-9 is extremely stable, raising the melting temperature (Tm) of CED-9 by 25°C, and that the binding surface of CED-9 extends beyond the BH3-binding region and reaches the BH4 domain. Consistently, the Tm and a 1H-15N correlation NMR spectrum of CED-9 in complex with EGL-1 are drastically different from those of CED-9 in complex with the EGL-1 BH3 peptide. The data suggest that the recognition between other BCL-2 family members may also involve much wider protein surfaces than is previously thought.
Bibliographical noteFunding Information:
We thank Professors J Ahnn (KJIST) and J Lee (Yonsei University) for providing the C. elegance cDNA library. This study used the beamline 6B at the Pohang Accelerator Laboratory and was supported by Creative Research Initiatives (to B-HO) and by the National Research Laboratory program (M1-0203-00-0020) (to WL) of the Korean Ministry of Science and Technology. J-SW, J-SJ, and N-CH were supported by the Brain Korea 21 Project.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology