1
|
Frascogna F, Ledermann B, Hartmann J, Pérez Patallo E, Zeqiri F, Hofmann E, Frankenberg-Dinkel N. On the evolution of the plant phytochrome chromophore biosynthesis. PLANT PHYSIOLOGY 2023; 193:246-258. [PMID: 37311159 DOI: 10.1093/plphys/kiad327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 05/25/2023] [Accepted: 05/29/2023] [Indexed: 06/15/2023]
Abstract
Phytochromes are biliprotein photoreceptors present in plants, algae, certain bacteria, and fungi. Land plant phytochromes use phytochromobilin (PΦB) as the bilin chromophore. Phytochromes of streptophyte algae, the clade within which land plants evolved, employ phycocyanobilin (PCB), leading to a more blue-shifted absorption spectrum. Both chromophores are synthesized by ferredoxin-dependent bilin reductases (FDBRs) starting from biliverdin IXα (BV). In cyanobacteria and chlorophyta, BV is reduced to PCB by the FDBR phycocyanobilin:ferredoxin oxidoreductase (PcyA), whereas, in land plants, BV is reduced to PФB by phytochromobilin synthase (HY2). However, phylogenetic studies suggested the absence of any ortholog of PcyA in streptophyte algae and the presence of only PФB biosynthesis-related genes (HY2). The HY2 of the streptophyte alga Klebsormidium nitens (formerly Klebsormidium flaccidum) has already indirectly been indicated to participate in PCB biosynthesis. Here, we overexpressed and purified a His6-tagged variant of K. nitens HY2 (KflaHY2) in Escherichia coli. Employing anaerobic bilin reductase activity assays and coupled phytochrome assembly assays, we confirmed the product and identified intermediates of the reaction. Site-directed mutagenesis revealed 2 aspartate residues critical for catalysis. While it was not possible to convert KflaHY2 into a PΦB-producing enzyme by simply exchanging the catalytic pair, the biochemical investigation of 2 additional members of the HY2 lineage enabled us to define 2 distinct clades, the PCB-HY2 and the PΦB-HY2 clade. Overall, our study gives insight into the evolution of the HY2 lineage of FDBRs.
Collapse
Affiliation(s)
- Federica Frascogna
- Department of Microbiology, University of Kaiserslautern-Landau, Kaiserslautern 67663, Germany
| | - Benjamin Ledermann
- Department of Microbiology, University of Kaiserslautern-Landau, Kaiserslautern 67663, Germany
| | - Jana Hartmann
- Department of Microbiology, University of Kaiserslautern-Landau, Kaiserslautern 67663, Germany
| | - Eugenio Pérez Patallo
- Department of Microbiology, University of Kaiserslautern-Landau, Kaiserslautern 67663, Germany
| | - Fjoralba Zeqiri
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum 44780, Germany
| | - Eckhard Hofmann
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum 44780, Germany
| | | |
Collapse
|
2
|
Guo R, Wang S, Niu NN, Xu YL, Zhu JX, Scheer H, Noy D, Zhao KH. Dichromic Allophycocyanin Trimer Covering a Broad Spectral Range (550-660 nm). Chemistry 2023; 29:e202203367. [PMID: 36382427 DOI: 10.1002/chem.202203367] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/17/2022]
Abstract
Phycobilisomes, the light-harvesting complexes of cyanobacteria and red algae, are a resource for photosynthetic, photonic and fluorescence labeling elements. They cover an exceptionally broad spectral range, but the complex superstructure and assembly have been an obstacle. By replacing in Synechocystis sp. PCC 6803 the biliverdin reductases, we studied the role of chromophores in the assembly of the phycobilisome core. Introduction of the green-absorbing phycoerythrobilin instead of the red-absorbing phycocyanobilin inhibited aggregation. A novel, trimeric allophycocyanin (Dic-APC) was obtained. In the small (110 kDa) unit, the two chromophores, phycoerythrobilin and phytochromobilin, cover a wide spectral range (550 to 660 nm). Due to efficient energy transfer, it provides an efficient artificial light-harvesting element. Dic-APC was generated in vitro by using the contained core-linker, LC , for template-assisted purification and assembly. Labeling the linker provides a method for targeting Dic-APC.
Collapse
Affiliation(s)
- Rui Guo
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Si Wang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Nan-Nan Niu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Ya-Li Xu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Jun-Xun Zhu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Hugo Scheer
- Department Biologie I, Universität München, Menzinger Str. 67, D-80638, München, Germany
| | - Dror Noy
- MIGAL-Galilee Research Institute S. Industrial Zone, Kiryat Shmona, Israel.,Faculty of Sciences and Technology, Tel-Hai Academic College, Upper Galilee, Israel
| | - Kai-Hong Zhao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| |
Collapse
|
3
|
Jacobson TB, Callaghan MM, Amador-Noguez D. Hostile Takeover: How Viruses Reprogram Prokaryotic Metabolism. Annu Rev Microbiol 2021; 75:515-539. [PMID: 34348026 DOI: 10.1146/annurev-micro-060621-043448] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To reproduce, prokaryotic viruses must hijack the cellular machinery of their hosts and redirect it toward the production of viral particles. While takeover of the host replication and protein synthesis apparatus has long been considered an essential feature of infection, recent studies indicate that extensive reprogramming of host primary metabolism is a widespread phenomenon among prokaryotic viruses that is required to fulfill the biosynthetic needs of virion production. In this review we provide an overview of the most significant recent findings regarding virus-induced reprogramming of prokaryotic metabolism and suggest how quantitative systems biology approaches may be used to provide a holistic understanding of metabolic remodeling during lytic viral infection. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Collapse
Affiliation(s)
- Tyler B Jacobson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , .,Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin 53726, USA.,Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Melanie M Callaghan
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , .,Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , .,Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin 53726, USA.,Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| |
Collapse
|
4
|
Campbell IJ, Olmos JL, Xu W, Kahanda D, Atkinson JT, Sparks ON, Miller MD, Phillips GN, Bennett GN, Silberg JJ. Prochlorococcus phage ferredoxin: structural characterization and electron transfer to cyanobacterial sulfite reductases. J Biol Chem 2020; 295:10610-10623. [PMID: 32434930 DOI: 10.1074/jbc.ra120.013501] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 05/15/2020] [Indexed: 01/13/2023] Open
Abstract
Marine cyanobacteria are infected by phages whose genomes encode ferredoxin (Fd) electron carriers. These Fds are thought to redirect the energy harvested from light to phage-encoded oxidoreductases that enhance viral fitness, but it is unclear how the biophysical properties and partner specificities of phage Fds relate to those of photosynthetic organisms. Here, results of a bioinformatics analysis using a sequence similarity network revealed that phage Fds are most closely related to cyanobacterial Fds that transfer electrons from photosystems to oxidoreductases involved in nutrient assimilation. Structural analysis of myovirus P-SSM2 Fd (pssm2-Fd), which infects the cyanobacterium Prochlorococcus marinus, revealed high levels of similarity to cyanobacterial Fds (root mean square deviations of ≤0.5 Å). Additionally, pssm2-Fd exhibited a low midpoint reduction potential (-336 mV versus a standard hydrogen electrode), similar to other photosynthetic Fds, although it had lower thermostability (Tm = 28 °C) than did many other Fds. When expressed in an Escherichia coli strain deficient in sulfite assimilation, pssm2-Fd complemented bacterial growth when coexpressed with a P. marinus sulfite reductase, revealing that pssm2-Fd can transfer electrons to a host protein involved in nutrient assimilation. The high levels of structural similarity with cyanobacterial Fds and reactivity with a host sulfite reductase suggest that phage Fds evolved to transfer electrons to cyanobacterially encoded oxidoreductases.
Collapse
Affiliation(s)
- Ian J Campbell
- Biochemistry and Cell Biology Graduate Program, Rice University, Houston, Texas, USA.,Department of Biosciences, Rice University, Houston, Texas, USA
| | - Jose Luis Olmos
- Biochemistry and Cell Biology Graduate Program, Rice University, Houston, Texas, USA.,Department of Biosciences, Rice University, Houston, Texas, USA
| | - Weijun Xu
- Department of Biosciences, Rice University, Houston, Texas, USA
| | | | | | | | | | - George N Phillips
- Department of Biosciences, Rice University, Houston, Texas, USA.,Department of Chemistry, Rice University, Houston, Texas, USA
| | - George N Bennett
- Department of Biosciences, Rice University, Houston, Texas, USA.,Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, USA
| | - Jonathan J Silberg
- Department of Biosciences, Rice University, Houston, Texas, USA .,Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, USA.,Department of Bioengineering, Rice University, Houston, Texas, USA
| |
Collapse
|
5
|
Sugishima M, Wada K, Fukuyama K, Yamamoto K. Crystal structure of phytochromobilin synthase in complex with biliverdin IXα, a key enzyme in the biosynthesis of phytochrome. J Biol Chem 2020; 295:771-782. [PMID: 31822504 DOI: 10.1074/jbc.ra119.011431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/08/2019] [Indexed: 11/06/2022] Open
Abstract
Phytochromobilin (PΦB) is a red/far-red light sensory pigment in plant phytochrome. PΦB synthase is a ferredoxin-dependent bilin reductase (FDBR) that catalyzes the site-specific reduction of bilins, which are sensory and photosynthesis pigments, and produces PΦB from biliverdin, a heme-derived linear tetrapyrrole pigment. Here, we determined the crystal structure of tomato PΦB synthase in complex with biliverdin at 1.95 Å resolution. The overall structure of tomato PΦB synthase was similar to those of other FDBRs, except for the addition of a long C-terminal loop and short helices. The structure further revealed that the C-terminal loop is part of the biliverdin-binding pocket and that two basic residues in the C-terminal loop form salt bridges with the propionate groups of biliverdin. This suggested that the C-terminal loop is involved in the interaction with ferredoxin and biliverdin. The configuration of biliverdin bound to tomato PΦB synthase differed from that of biliverdin bound to other FDBRs, and its orientation in PΦB synthase was inverted relative to its orientation in the other FDBRs. Structural and enzymatic analyses disclosed that two aspartic acid residues, Asp-123 and Asp-263, form hydrogen bonds with water molecules and are essential for the site-specific A-ring reduction of biliverdin. On the basis of these observations and enzymatic assays with a V121A PΦB synthase variant, we propose the following mechanistic product release mechanism: PΦB synthase-catalyzed stereospecific reduction produces 2(R)-PΦB, which when bound to PΦB synthase collides with the side chain of Val-121, releasing 2(R)-PΦB from the synthase.
Collapse
Affiliation(s)
- Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Ken Yamamoto
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| |
Collapse
|
6
|
Sugishima M, Wada K, Fukuyama K, Yamamoto K. Crystal structure of phytochromobilin synthase in complex with biliverdin IXα, a key enzyme in the biosynthesis of phytochrome. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49934-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
|
7
|
Zimmerman AE, Howard-Varona C, Needham DM, John SG, Worden AZ, Sullivan MB, Waldbauer JR, Coleman ML. Metabolic and biogeochemical consequences of viral infection in aquatic ecosystems. Nat Rev Microbiol 2019; 18:21-34. [PMID: 31690825 DOI: 10.1038/s41579-019-0270-x] [Citation(s) in RCA: 155] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2019] [Indexed: 12/23/2022]
Abstract
Ecosystems are controlled by 'bottom-up' (resources) and 'top-down' (predation) forces. Viral infection is now recognized as a ubiquitous top-down control of microbial growth across ecosystems but, at the same time, cell death by viral predation influences, and is influenced by, resource availability. In this Review, we discuss recent advances in understanding the biogeochemical impact of viruses, focusing on how metabolic reprogramming of host cells during lytic viral infection alters the flow of energy and nutrients in aquatic ecosystems. Our synthesis revealed several emerging themes. First, viral infection transforms host metabolism, in part through virus-encoded metabolic genes; the functions performed by these genes appear to alleviate energetic and biosynthetic bottlenecks to viral production. Second, viral infection depends on the physiological state of the host cell and on environmental conditions, which are challenging to replicate in the laboratory. Last, metabolic reprogramming of infected cells and viral lysis alter nutrient cycling and carbon export in the oceans, although the net impacts remain uncertain. This Review highlights the need for understanding viral infection dynamics in realistic physiological and environmental contexts to better predict their biogeochemical consequences.
Collapse
Affiliation(s)
- Amy E Zimmerman
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | | | - David M Needham
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - Seth G John
- Department of Earth Science, University of Southern California, Los Angeles, CA, USA
| | - Alexandra Z Worden
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA.,Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
| | - Matthew B Sullivan
- Department of Microbiology, Ohio State University, Columbus, OH, USA.,Department of Civil, Environmental and Geodetic Engineering, Ohio State University, Columbus, OH, USA
| | - Jacob R Waldbauer
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | - Maureen L Coleman
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA.
| |
Collapse
|
8
|
Sommerkamp JA, Frankenberg-Dinkel N, Hofmann E. Crystal structure of the first eukaryotic bilin reductase GtPEBB reveals a flipped binding mode of dihydrobiliverdin. J Biol Chem 2019; 294:13889-13901. [PMID: 31366727 PMCID: PMC6755814 DOI: 10.1074/jbc.ra119.009306] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/26/2019] [Indexed: 01/11/2023] Open
Abstract
Phycobilins are light-harvesting pigments of cyanobacteria, red algae, and cryptophytes. The biosynthesis of phycoerythrobilin (PEB) is catalyzed by the subsequent action of two ferredoxin-dependent bilin reductases (FDBRs). Although 15,16-dihydrobiliverdin (DHBV):ferredoxin oxidoreductase (PebA) catalyzes the two-electron reduction of biliverdin IXα to 15,16-DHBV, PEB:ferredoxin oxidoreductase (PebB) reduces this intermediate further to PEB. Interestingly, marine viruses encode the FDBR PebS combining both activities within one enzyme. Although PebA and PebS share a canonical fold with similar substrate-binding pockets, the structural determinants for the stereo- and regiospecific modification of their tetrapyrrole substrates are incompletely understood, also because of the lack of a PebB structure. Here, we solved the X-ray crystal structures of both substrate-free and -bound PEBB from the cryptophyte Guillardia theta at 1.90 and 1.65 Å, respectively. The structures of PEBB exhibit the typical α/β/α-sandwich fold. Interestingly, the open-chain tetrapyrrole substrate DHBV is bound in an unexpected flipped orientation within the canonical FDBR active site. Biochemical analyses of the WT enzyme and active site variants identified two central aspartate residues Asp-99 and Asp-219 as essential for catalytic activity. In addition, the conserved Arg-215 plays a critical role in substrate specificity, binding orientation, and active site integrity. Because these critical residues are conserved within certain FDBRs displaying A-ring reduction activity, we propose that they present a conserved mechanism for this reaction. The flipped substrate-binding mode indicates that two-electron reducing FDBRs utilize the same primary site within the binding pocket and that substrate orientation is the determinant for A- or D-ring regiospecificity.
Collapse
Affiliation(s)
- Johannes A Sommerkamp
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nicole Frankenberg-Dinkel
- Department of Biology, Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Eckhard Hofmann
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44801 Bochum, Germany
| |
Collapse
|
9
|
Aras M, Hartmann V, Hartmann J, Nowaczyk MM, Frankenberg-Dinkel N. Proximity channeling during cyanobacterial phycoerythrobilin synthesis. FEBS J 2019; 287:284-294. [PMID: 31319014 DOI: 10.1111/febs.15003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/17/2019] [Accepted: 07/16/2019] [Indexed: 11/30/2022]
Abstract
Substrate channeling is a widespread mechanism in metabolic pathways to avoid decomposition of unstable intermediates, competing reactions, and to accelerate catalytic turnover. During the biosynthesis of light-harvesting phycobilins in cyanobacteria, two members of the ferredoxin-dependent bilin reductases are involved in the reduction of the open-chain tetrapyrrole biliverdin IXα to the pink pigment phycoerythrobilin. The first reaction is catalyzed by 15,16-dihydrobiliverdin:ferredoxin oxidoreductase and produces the unstable intermediate 15,16-dihydrobiliverdin (DHBV). This intermediate is subsequently converted by phycoerythrobilin:ferredoxin oxidoreductase to the final product phycoerythrobilin. Although substrate channeling has been postulated already a decade ago, detailed experimental evidence was missing. Using a new on-column assay employing immobilized enzyme in combination with UV-Vis and fluorescence spectroscopy revealed that both enzymes transiently interact and that transfer of the intermediate is facilitated by a significantly higher binding affinity of DHBV toward phycoerythrobilin:ferredoxin oxidoreductase. Concluding from the presented data, the intermediate DHBV is transferred via proximity channeling.
Collapse
Affiliation(s)
- Marco Aras
- Fachbereich Biologie, Abteilung für Mikrobiologie, Technische Universität Kaiserslautern, Germany
| | - Volker Hartmann
- Cyanobakterielle Membranprotein Komplexe, Fakultät für Biologie und Biotechnologie, Ruhr-Universität Bochum, Germany
| | - Jana Hartmann
- Fachbereich Biologie, Abteilung für Mikrobiologie, Technische Universität Kaiserslautern, Germany
| | - Marc M Nowaczyk
- Cyanobakterielle Membranprotein Komplexe, Fakultät für Biologie und Biotechnologie, Ruhr-Universität Bochum, Germany
| | | |
Collapse
|
10
|
Sugishima M, Wada K, Unno M, Fukuyama K. Bilin-metabolizing enzymes: site-specific reductions catalyzed by two different type of enzymes. Curr Opin Struct Biol 2019; 59:73-80. [PMID: 30954759 DOI: 10.1016/j.sbi.2019.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 01/09/2019] [Accepted: 03/04/2019] [Indexed: 02/05/2023]
Abstract
In mammals, the green heme metabolite biliverdin is converted to a yellow anti-oxidant by NAD(P)H-dependent biliverdin reductase (BVR), whereas in O2-dependent photosynthetic organisms it is converted to photosynthetic or light-sensing pigments by ferredoxin-dependent bilin reductases (FDBRs). In NADP+-bound and biliverdin-bound BVR-A, two biliverdins are stacked at the binding cleft; one is positioned to accept hydride from NADPH, and the other appears to donate a proton to the first biliverdin through a neighboring arginine residue. During the FDBR-catalyzed reaction, electrons and protons are supplied to bilins from ferredoxin and from FDBRs and waters bound within FDBRs, respectively. Thus, the protonation sites of bilin and catalytic residues are important for the analysis of site-specific reduction. The neutron structure of FDBR sheds light on this issue.
Collapse
Affiliation(s)
- Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan.
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Masaki Unno
- Graduate School of Science and Engineering, Ibaraki University, Ibaraki 316-8511, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| |
Collapse
|