1I3S

THE 2.7 ANGSTROM RESOLUTION CRYSTAL STRUCTURE OF A MUTATED BACULOVIRUS P35 AFTER CASPASE CLEAVAGE

Summary for 1I3S

• Entry DOI: 10.2210/pdb1i3s/pdb
• Related: 1I3P 1p35
• Descriptor: EARLY 35 KDA PROTEIN, 2,3-DIHYDROXY-1,4-DITHIOBUTANE (3 entities in total)
• Functional Keywords: hairpin loop, helix-turn-helix, reactive site loop, apoptosis
• Biological source: Autographa californica nucleopolyhedrovirus
• Total number of polymer chains: 3
• Total formula weight: 104693.29

Authors

dela Cruz, W.P.,Lemongello, D.,Friesen, P.D.,Fisher, A.J. (deposition date: 2001-02-15, release date: 2001-10-24, Last modification date: 2024-10-30)

Primary citation

dela Cruz, W.P.,Friesen, P.D.,Fisher, A.J.
Crystal structure of baculovirus P35 reveals a novel conformational change in the reactive site loop after caspase cleavage.
J.Biol.Chem., 276:32933-32939, 2001

PubMed Abstract: Baculovirus P35 is a universal suppressor of apoptosis that stoichiometrically inhibits cellular caspases in a novel cleavage-dependent mechanism. Upon caspase cleavage at Asp-87, the 10- and 25-kDa cleavage products of P35 remain tightly associated with the inhibited caspase. Mutations in the alpha-helix of the reactive site loop preceding the cleavage site abrogate caspase inhibition and antiapoptotic activity. Substitution of Pro for Val-71, which is located in the middle of this alpha-helix, produces a protein that is cleaved at the requisite Asp-87 but does not remain bound to the caspase. This loss-of-function mutation provided the opportunity to structurally analyze the conformational changes of the P35 reactive site loop after caspase cleavage. We report here the 2.7 A resolution crystal structure of V71P-mutated P35 after cleavage by human caspase-3. The structure reveals a large movement in the carboxyl-terminal side of the reactive site loop that swings down and forms a new beta-strand that augments an existing beta-sheet. Additionally, the hydrophobic amino terminus releases and extends away from the protein core. Similar movements occur when P35 forms an inhibitory complex with human caspase-8. These findings suggest that the alpha-helix mutation may alter the sequential steps or kinetics of the conformational changes required for inhibition, thereby causing P35 loss of function.

PubMed: 11402050
DOI: 10.1074/jbc.M103930200

Experimental method

X-RAY DIFFRACTION (2.7 Å)