The crystal structure of the C-terminal DAP5/p97 domain sheds light on the molecular basis for its processing by caspase cleavage.
DAP5/p97 (death-associated protein 5) is a member of the eukaryotic translation initiation factor 4G family. It functions as a scaffold protein promoting cap-independent translation of proteins. During apoptosis, DAP5/p97 is cleaved by caspases at position 792, yielding an 86-kDa C-terminal truncated isoform (DAP5/p86) that promotes translation of several mRNAs mediated by an internal ribosome entry site. In this study, we report the crystal structure of the C-terminal region of DAP5/p97 extending between amino acids 730 and 897. This structure consists of four HEAT-Repeats and is homologous to the C-terminal domain of eIF4GI, eIF5, and eIF2Bepsilon. Unlike the other proteins, DAP5/p97 lacks electron density in the loop connecting alpha3 and alpha4, which harbors the caspase cleavage site. Moreover, we observe fewer interactions between these two helices. Thus, previous mapping of this site by mutation analysis is confirmed here by the resolved structure of the DAP5/p97 C-terminus. In addition, we identified the position of two conserved aromatic and acidic boxes in the structure of the DAP5/p97 C-terminus. The acidic residues in the two aromatic and acidic boxes form a continuous negatively charged patch, which is suggested to make specific interactions with other proteins such as eIF2beta. The caspase cleavage of DAP5/p97 removes the subdomain carrying acidic residues in the AA-box motif, which may result in exposure of a hydrophobic surface. These intriguing structural differences between the two DAP5 isoforms suggest that they have different interaction partners and, subsequently, different functions.
Liberman
Noa
N
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
Dym
Orly
O
Unger
Tamar
T
Albeck
Shira
S
Peleg
Yoav
Y
Jacobovitch
Yossi
Y
Branzburg
Anna
A
Eisenstein
Miriam
M
Marash
Lea
L
Kimchi
Adi
A
D000595:Amino Acid Sequence; D020169:Caspases / Q000378:metabolism*; D018360:Crystallography, X-Ray; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D055672:Static Electricity
C491300:EIF4G2 protein, human; D039603:Eukaryotic Initiation Factor-4G; D011994:Recombinant Proteins; D020169:Caspases