4nt1
Crystal structure of apo-form of Arabidopsis ACD11 (accelerated-cell-death 11) at 1.8 Angstrom resolution
Structural highlights
FunctionACD11_ARATH Exhibits selective intermembrane transfer of ceramide-1-phosphate (C1P) and phytoceramide-1-phosphate (PubMed:24412362, PubMed:28011644). Does not transport ceramide (Cer) or GalCer, suggesting a requirement for phosphate in the headgroup for functionality (PubMed:24412362). Transports in vitro sphingosine, but not glycosphingolipids (PubMed:11850411). Has also some in vitro activity with sphingomyelin, a lipid not detected in plant tissues (PubMed:18657186). The transport function may be not directly involved in regulating cell death. Rather, perturbations in the function of ACD11 or related components could be monitored by R-proteins, which then mediate defense and programmed cell death (PCD), as proposed in the guard hypothesis (Probable). C1P transfer is stimulated by phosphatidylserine in C1P source vesicles (PubMed:28011644). Regulates autophagy, inflammasome mediated IL1B and IL18 processing, and pyroptosis, but not apoptosis (PubMed:28011644).[1] [2] [3] [4] [5] Publication Abstract from PubMedThe accelerated cell death 11 (acd11) mutant of Arabidopsis provides a genetic model for studying immune response activation and localized cellular suicide that halt pathogen spread during infection in plants. Here, we elucidate ACD11 structure and function and show that acd11 disruption dramatically alters the in vivo balance of sphingolipid mediators that regulate eukaryotic-programmed cell death. In acd11 mutants, normally low ceramide-1-phosphate (C1P) levels become elevated, but the relatively abundant cell death inducer phytoceramide rises acutely. ACD11 exhibits selective intermembrane transfer of C1P and phyto-C1P. Crystal structures establish C1P binding via a surface-localized, phosphate headgroup recognition center connected to an interior hydrophobic pocket that adaptively ensheaths lipid chains via a cleft-like gating mechanism. Point mutation mapping confirms functional involvement of binding site residues. A pi helix (pi bulge) near the lipid binding cleft distinguishes apo-ACD11 from other GLTP folds. The global two-layer, alpha-helically dominated, "sandwich" topology displaying C1P-selective binding identifies ACD11 as the plant prototype of a GLTP fold subfamily. Arabidopsis Accelerated Cell Death 11, ACD11, Is a Ceramide-1-Phosphate Transfer Protein and Intermediary Regulator of Phytoceramide Levels.,Simanshu DK, Zhai X, Munch D, Hofius D, Markham JE, Bielawski J, Bielawska A, Malinina L, Molotkovsky JG, Mundy JW, Patel DJ, Brown RE Cell Rep. 2014 Jan 30;6(2):388-99. doi: 10.1016/j.celrep.2013.12.023. Epub 2014, Jan 9. PMID:24412362[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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