| Structural highlights
Function
ADO1_ARATH Component of an E3 ubiquitin ligase complex that plays a central role in blue light-dependent circadian cycles. Acts as a blue light photoreceptor, due to the presence of FMN, that mediates light-regulated protein degradation of critical clock components by targeting them to the proteasome complex. The SCF(ADO1) E3 ubiquitin ligase complex is involved in the regulation of circadian clock-dependent processes including the transition to flowering time, hypocotyl elongation, cotyledons and leaf movement rhythms. APRR1/TOC1 and APRR5, but not 'GIGANTEA', are proteolytic substrates of this ubiquitin ligase complex. Blue light enhances cooperative stabilization of 'GIGANTEA' and ADO1/ZTL, leading to amplification and sharpening of the expression profile of APRR1/TOC1. ADO1/ZTL interacts with ADO3, preventing the interaction of ADO3 with CDF1.[1] [2] [3] [4] [5] [6] [7] [8] [9]
Publication Abstract from PubMed
A LOV (Light, Oxygen, or Voltage) domain containing blue-light photoreceptor ZEITLUPE (ZTL) directs circadian timing by degrading clock proteins in plants. Functions hinge upon allosteric differences coupled to the ZTL photocycle; however, structural and kinetic information was unavailable. Herein, we tune the ZTL photocycle over two orders of magnitude. These variants reveal that ZTL complexes with targets independent of light, but dictates enhanced protein degradation in the dark. In vivo experiments definitively show photocycle kinetics dictate the rate of clock component degradation, thereby impacting circadian period. Structural studies demonstrate that photocycle dependent activation of ZTL depends on an unusual dark-state conformation of ZTL. Crystal structures of ZTL LOV domain confirm delineation of structural and kinetic mechanisms and identify an evolutionarily selected allosteric hinge differentiating modes of PAS/LOV signal transduction. The combined biochemical, genetic and structural studies provide new mechanisms indicating how PAS/LOV proteins integrate environmental variables in complex networks.
Kinetics of the LOV domain of ZEITLUPE determine its circadian function in Arabidopsis.,Pudasaini A, Shim JS, Song YH, Shi H, Kiba T, Somers DE, Imaizumi T, Zoltowski BD Elife. 2017 Feb 28;6. pii: e21646. doi: 10.7554/eLife.21646. PMID:28244872[10]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Somers DE, Schultz TF, Milnamow M, Kay SA. ZEITLUPE encodes a novel clock-associated PAS protein from Arabidopsis. Cell. 2000 Apr 28;101(3):319-29. PMID:10847686
- ↑ Nelson DC, Lasswell J, Rogg LE, Cohen MA, Bartel B. FKF1, a clock-controlled gene that regulates the transition to flowering in Arabidopsis. Cell. 2000 Apr 28;101(3):331-40. PMID:10847687
- ↑ Kiyosue T, Wada M. LKP1 (LOV kelch protein 1): a factor involved in the regulation of flowering time in arabidopsis. Plant J. 2000 Sep;23(6):807-15. PMID:10998191
- ↑ Jarillo JA, Capel J, Tang RH, Yang HQ, Alonso JM, Ecker JR, Cashmore AR. An Arabidopsis circadian clock component interacts with both CRY1 and phyB. Nature. 2001 Mar 22;410(6827):487-90. PMID:11260718 doi:https://dx.doi.org/10.1038/35068589
- ↑ Somers DE, Kim WY, Geng R. The F-box protein ZEITLUPE confers dosage-dependent control on the circadian clock, photomorphogenesis, and flowering time. Plant Cell. 2004 Mar;16(3):769-82. Epub 2004 Feb 18. PMID:14973171 doi:https://dx.doi.org/10.1105/tpc.016808
- ↑ Han L, Mason M, Risseeuw EP, Crosby WL, Somers DE. Formation of an SCF(ZTL) complex is required for proper regulation of circadian timing. Plant J. 2004 Oct;40(2):291-301. PMID:15447654 doi:https://dx.doi.org/10.1111/j.1365-313X.2004.02207.x
- ↑ Kevei E, Gyula P, Hall A, Kozma-Bognar L, Kim WY, Eriksson ME, Toth R, Hanano S, Feher B, Southern MM, Bastow RM, Viczian A, Hibberd V, Davis SJ, Somers DE, Nagy F, Millar AJ. Forward genetic analysis of the circadian clock separates the multiple functions of ZEITLUPE. Plant Physiol. 2006 Mar;140(3):933-45. Epub 2006 Jan 20. PMID:16428597 doi:https://dx.doi.org/10.1104/pp.105.074864
- ↑ Kim WY, Fujiwara S, Suh SS, Kim J, Kim Y, Han L, David K, Putterill J, Nam HG, Somers DE. ZEITLUPE is a circadian photoreceptor stabilized by GIGANTEA in blue light. Nature. 2007 Sep 20;449(7160):356-60. Epub 2007 Aug 19. PMID:17704763 doi:https://dx.doi.org/10.1038/nature06132
- ↑ Takase T, Nishiyama Y, Tanihigashi H, Ogura Y, Miyazaki Y, Yamada Y, Kiyosue T. LOV KELCH PROTEIN2 and ZEITLUPE repress Arabidopsis photoperiodic flowering under non-inductive conditions, dependent on FLAVIN-BINDING KELCH REPEAT F-BOX1. Plant J. 2011 Aug;67(4):608-21. doi: 10.1111/j.1365-313X.2011.04618.x. Epub 2011 , Jul 14. PMID:21518052 doi:https://dx.doi.org/10.1111/j.1365-313X.2011.04618.x
- ↑ Pudasaini A, Shim JS, Song YH, Shi H, Kiba T, Somers DE, Imaizumi T, Zoltowski BD. Kinetics of the LOV domain of ZEITLUPE determine its circadian function in Arabidopsis. Elife. 2017 Feb 28;6. pii: e21646. doi: 10.7554/eLife.21646. PMID:28244872 doi:https://dx.doi.org/10.7554/eLife.21646
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