Solution structure of the DFF-C domain of DFF45/ICAD. A structural basis for the regulation of apoptotic DNA fragmentation.
DFF45/ICAD has dual functions in the final stage of apoptosis, by acting as both a folding chaperone and a DNase inhibitor of DFF40/CAD. Here, we present the solution structure of the C-terminal domain of DFF45, which is essential for its chaperone-like activity. The structure of this domain (DFF-C) consists of four alpha helices, which are folded in a novel helix-packing arrangement. The 3D structure reveals a large cluster of negatively charged residues on the molecular surface of DFF-C. This observation suggests that charge complementation plays an important role in the interaction of DFF-C with the positively charged catalytic domain of DFF40, and thus for the chaperone activity of DFF45. The structure of DFF-C also provides a rationale for the loss of the chaperone activity in DFF35, a short isoform of DFF45. Indeed, in DFF35, the amino acid sequence is truncated in the middle of the second alpha helix constituting the structure of DFF-C, and thus both the hydrophobic core and the cluster of negative charges are disrupted.
Fukushima
Kay
K
Protein Research Group, Genomic Sciences Center, RIKEN Yokohama Institute, 1-7-22, Suehiro-cho, Tsurumi, Yokohama, Kanagawa, Japan.
Kikuchi
Jun
J
Koshiba
Seizo
S
Kigawa
Takanori
T
Kuroda
Yutaka
Y
Yokoyama
Shigeyuki
S
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002942:Circular Dichroism; D053938:DNA Fragmentation; D006367:HeLa Cells; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D012996:Solutions; D055672:Static Electricity; D013329:Structure-Activity Relationship
D051017:Apoptosis Regulatory Proteins; D018832:Molecular Chaperones; D011506:Proteins; D012996:Solutions; C109664:caspase-activated DNase inhibitor; D006859:Hydrogen