5mz6
Cryo-EM structure of a Separase-Securin complex from Caenorhabditis elegans at 3.8 A resolution
Structural highlights
FunctionSEP1_CAEEL Cysteine protease, which plays a central role in homologous chromosome separation during meiosis I and in sister chromatid separation during embryonic mitosis (PubMed:11728305, PubMed:12498686, PubMed:20116245, PubMed:21878498). Promotes chromosome/sister chromatid segregation by cleaving the scc-1 (mitosis) and rec-8 (meiosis) subunits of the cohesin complex at the onset of anaphase (Probable). May cleave histone H3-like protein cpar-1 during meiosis I metaphase-anaphase transition (PubMed:25919583). Promotes cortical granule exocytosis after oocyte fertilization during the first meiotic anaphase (PubMed:17913784, PubMed:21878498). Essential for embryonic cytokinesis by regulating rab-11-positive vesicle trafficking at the plasma membrane at the cleavage furrow and midbody (PubMed:20116245). Regulates centriole segregation during spermatocyte meiosis (PubMed:23401519). Required for embryonic anterior-posterior axis formation (PubMed:11832245).[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedSeparase is a caspase-family protease that initiates chromatid segregation by cleaving the kleisin subunits (Scc1 and Rec8) of cohesin, and regulates centrosome duplication and mitotic spindle function through cleavage of kendrin and Slk19. To understand the mechanisms of securin regulation of separase, we used single-particle cryo-electron microscopy (cryo-EM) to determine a near-atomic-resolution structure of the Caenorhabditis elegans separase-securin complex. Separase adopts a triangular-shaped bilobal architecture comprising an N-terminal tetratricopeptide repeat (TPR)-like alpha-solenoid domain docked onto the conserved C-terminal protease domain. Securin engages separase in an extended antiparallel conformation, interacting with both lobes. It inhibits separase by interacting with the catalytic site through a pseudosubstrate mechanism, thus revealing that in the inhibited separase-securin complex, the catalytic site adopts a conformation compatible with substrate binding. Securin is protected from cleavage because an aliphatic side chain at the P1 position represses protease activity by disrupting the organization of catalytic site residues. Cryo-EM structure of a metazoan separase-securin complex at near-atomic resolution.,Boland A, Martin TG, Zhang Z, Yang J, Bai XC, Chang L, Scheres SH, Barford D Nat Struct Mol Biol. 2017 Mar 6. doi: 10.1038/nsmb.3386. PMID:28263324[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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