Antiapoptotic Bcl-2 homolog CED-9 in Caenorhabditis elegans: Dynamics of BH3 and CED-4 binding regions and comparison with mammalian antiapoptotic Bcl-2 proteins

作者：Modi Vivek; Sankararamakrishnan Ramasubbu^*

来源：Proteins: Structure, Function, and Genetics , 2014, 82(6): 1035-1047.

DOI：10.1002/prot.24476

• protein-protein interactions in apoptosis
• hydrophobic binding groove
• accessible surface area
• flexible and rigid binding regions
• interhelical angle
• helix bundle protein
• programmed cell death
• comparative simulations

Proteins belonging to Bcl-2 family regulate intrinsic cell death pathway. Although mammalian antiapoptotic Bcl-2 members interact with multiple proapoptotic proteins, the Caenorhabditis elegans Bcl-2 homolog CED-9 is known to have only two proapoptotic partners. The BH3-motif of proapoptotic proteins bind to the hydrophobic groove of prosurvival proteins formed by the Bcl-2 helical fold. CED-9 is also known to interact with CED-4, a homolog of the human cell death activator Apaf1. We have performed molecular dynamics simulations of CED-9 in two forms and compared the results with those of mammalian counterparts Bcl-X-L, Bcl-w, and Bcl-2. Our studies demonstrate that the region forming the hydrophobic cleft is more flexible compared with the CED-4-binding region, and this is generally true for all antiapoptotic Bcl-2 proteins studied. CED-9 is the most stable protein during simulations and its hydrophobic pocket is relatively rigid explaining the absence of functional redundancy in CED-9. The BH3-binding region of Bcl-2 is less flexible among the mammalian proteins and this lends support to the studies that Bcl-2 binds to less number of BH3 peptides with high affinity. The C-terminal helix of CED-9 lost its helical character because of a large number of charged residues. We speculate that this region probably plays a role in intracellular localization of CED-9. The BH4-motif accessibility in CED-9 and Bcl-w is controlled by the loop connecting the first two helices. Although CED-9 adopts the same Bcl-2 fold, our studies highlight important differences in the dynamic behavior of CED-9 and mammalian antiapoptotic homologs. Proteins 2014; 82:1035-1047.

• 出版日期2014-6