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Publication Abstract from PubMed

Apoptosome assembly is highly regulated in the intrinsic cell death pathway. To better understand this step, we created an improved model of the human apoptosome using a crystal structure of full length Apaf-1 and a single particle, electron density map at approximately 9.5 A resolution. The apoptosome model includes N-terminal domains of Apaf-1, cognate beta-propellers, and cytochrome c. A direct comparison of Apaf-1 in the apoptosome and as a monomer reveals conformational changes that occur during the first two steps of assembly. This includes an induced-fit mechanism for cytochrome c binding to regulatory beta-propellers, which is dependent on shape and charge complementarity, and a large rotation of the nucleotide binding module during nucleotide exchange. These linked conformational changes create an extended Apaf-1 monomer and drive apoptosome assembly. Moreover, the N-terminal CARD in the inactive Apaf-1 monomer is not shielded from other proteins by beta-propellers. Hence, the Apaf-1 CARD may be free to interact with a procaspase-9 CARD either before or during apoptosome assembly. Irrespective of the timing, the end product of assembly is a holo-apoptosome with an acentric CARD-CARD disk and tethered pc-9 catalytic domains. Subsequent activation of pc-9 leads to a proteolytic cascade and cell death.

Changes in apaf-1 conformation that drive apoptosome assembly.,Yuan S, Topf M, Reubold TF, Eschenburg S, Akey CW Biochemistry. 2013 Apr 2;52(13):2319-27. doi: 10.1021/bi301721g. Epub 2013 Mar, 22. PMID:23521171^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.