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Stanovova MV, Gazizova GR, Gorbushin AM. Transcriptomic profiling of immune-associated molecules in the coelomocytes of lugworm Arenicola marina (Linnaeus, 1758). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2023; 340:34-55. [PMID: 35438249 DOI: 10.1002/jez.b.23135] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 02/04/2022] [Accepted: 03/11/2022] [Indexed: 12/16/2022]
Abstract
Organization and functioning of immune system remain unevenly studied in different taxa of lophotrochozoan animals. We analyzed transcriptomic data on coelomocytes of the lugworm Arenicola marina (Linnaeus, 1758; Annelida, Polychaeta) to gain insights into the molecular mechanisms involved in polychaete immunity. Coelomocytes are specialized motile cells populating coelomic fluid of annelids, responsible for cellular defense reactions and providing humoral immune factors. The transcriptome was enriched with immune-related transcripts by challenging the cells in vitro with lipopolysaccharides of Escherichia coli and Zymosan from Saccharomyces cerevisiae. Our analysis revealed a multifaceted and complex internal defense system of the lugworm. A. marina possesses orthologs of proto-complement-like factors: six thioester-containing proteins, a complement-like receptor, and a MASP-related serine protease (MReM2). A. marina coelomocytes employ pattern-recognition receptors to detect pathogens and regulate immune responses. Among them, there are 18 Toll-like receptors and various putative lectin-like proteins with evolutionary conserved and taxa-specific domains. C-type lectins and a novel family of Gal-binding and CUB domains containing receptors were the most abundant in the transcriptome. The array of pore-forming proteins in the coelomocytes was surprisingly reduced compared to that of other invertebrate species. We characterized a set of conserved proteins metabolizing reactive oxygen species and nitric oxide and expanded the arsenal of potential antimicrobial peptides. Phenoloxidase activity in immune cells of lugworm is mediated only by laccase enzyme. The described repertoire of immune-associated molecules provides valuable candidates for further functional and comparative research on the immunity of annelids.
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Affiliation(s)
- Maria V Stanovova
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Guzel R Gazizova
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - Alexander M Gorbushin
- Sechenov Institute of Evolutionary Physiology and Biochemistry (IEPhB RAS), St. Petersburg, Russia
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Therapeutic Potential of Hemoglobin Derived from the Marine Worm Arenicola marina (M101): A Literature Review of a Breakthrough Innovation. Mar Drugs 2021; 19:md19070376. [PMID: 34210070 PMCID: PMC8304559 DOI: 10.3390/md19070376] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 06/21/2021] [Accepted: 06/26/2021] [Indexed: 01/19/2023] Open
Abstract
Oxygen (O2) is indispensable for aerobic respiration and cellular metabolism. In case of injury, reactive oxygen species are produced, causing oxidative stress, which triggers cell damaging chemical mediators leading to ischemic reperfusion injuries (IRI). Sufficient tissue oxygenation is necessary for optimal wound healing. In this context, several hemoglobin-based oxygen carriers have been developed and tested, especially as graft preservatives for transplant procedures. However, most of the commercially available O2 carriers increase oxidative stress and show some adverse effects. Interestingly, the hemoglobin derived from the marine lugworm Arenicola marina (M101) has been presented as an efficient therapeutic O2 carrier with potential anti-inflammatory, anti-bacterial, and antioxidant properties. Furthermore, it has demonstrated promise as a supplement to conventional organ preservatives by reducing IRI. This review summarizes the properties and various applications of M101. M101 is an innovative oxygen carrier with several beneficial therapeutic properties, and further research must be carried out to determine its efficacy in the management of different pathologies.
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Green Etxabe A, Pini JM, Short S, Cunha L, Kille P, Watson GJ. Identifying conserved polychaete molecular markers of metal exposure: Comparative analyses using the Alitta virens (Annelida, Lophotrochozoa) transcriptome. Comp Biochem Physiol C Toxicol Pharmacol 2021; 240:108913. [PMID: 33164845 DOI: 10.1016/j.cbpc.2020.108913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/07/2020] [Accepted: 10/12/2020] [Indexed: 12/13/2022]
Abstract
Polychaetes are vital for evaluating the effects of toxic metals in marine systems, and sensitive molecular biomarkers should be integral to monitoring efforts. However, the few polychaete markers that exist are inconsistent, even within the same species, failing to identify gene expression changes in metal-exposed animals incurring clear metabolic costs. Comparing previously characterised polychaete metal-responsive genes with those of another carefully selected species could identify biomarkers applicable across polychaetes. The ragworm Alitta virens (Sars, 1835) is particularly suited for such comparisons due to its dominance of fully saline coastal areas, widespread distribution, large biomass, and its phylogenetic position relative to other polychaete 'omic' resources. A transcriptome atlas for A. virens was generated and an RNASeq-qPCR screening approach was used to characterise the response to chronic exposures of environmentally relevant concentrations of copper and zinc in controlled mesocosms. Genes presenting dramatic expression changes in A. virens were compared with known metal-responsive genes in other polychaetes to identify new possible biomarkers and assess those currently used. This revealed some current markers should probably be abandoned (e.g. Atox1), while others, such as GST-Omega, should be used with caution, as different polychaete species appear to upregulate distinct GST-Omega orthologues. In addition, the comparisons give some indication of genes that are induced by metal exposure across phylogenetically divergent polychaetes, including a suite of haemoglobin subunits and linker chains that could play conserved roles in metal-stress response. Although such newly identified markers need further characterisation, they offer alternatives to current markers that are plainly insufficient.
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Affiliation(s)
- Amaia Green Etxabe
- UK Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Wallingford, Oxfordshire OX10 8BB, UK
| | - Jennifer M Pini
- CP-Texinfine (France), 60 Rue Duguesclin, 69006 Lyon, France
| | - Stephen Short
- Cardiff School of Biosciences, Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AT, UK.
| | - Luis Cunha
- University of Coimbra, Centre for Functional Ecology, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal; School of Applied Sciences, University of South Wales, Pontypridd, Wales CF37 4BD, UK
| | - Peter Kille
- Cardiff School of Biosciences, Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AT, UK
| | - Gordon J Watson
- Institute of Marine Sciences, School of Biological Sciences, University of Portsmouth, Ferry Road, Portsmouth PO4 9LY, UK
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Recent Insights into the Diversity and Evolution of Invertebrate Hemerythrins and Extracellular Globins. Subcell Biochem 2020; 94:251-273. [PMID: 32189303 DOI: 10.1007/978-3-030-41769-7_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
There are three broad groups of oxygen-transport proteins found in the haemolymph (blood) of invertebrates, namely the hemocyanins, the hemerythrins and the globins. Both hemerythrins and extracellular globins are iron-based proteins that are understudied when compared to the copper-containing hemocyanins. Recent evidence suggests that hemerythrins and (giant) extracellular globins (and their linker chains) are more widely distributed than previously thought and may have biological functions beyond oxygen transport and storage. Herein, we review contemporary literature of these often-neglected proteins with respect to their structural configurations on formation and ancestral states.
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Belato FA, Schrago CG, Coates CJ, Halanych KM, Costa-Paiva EM. Newly Discovered Occurrences and Gene Tree of the Extracellular Globins and Linker Chains from the Giant Hexagonal Bilayer Hemoglobin in Metazoans. Genome Biol Evol 2019; 11:597-612. [PMID: 30668717 PMCID: PMC6400237 DOI: 10.1093/gbe/evz012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2019] [Indexed: 02/07/2023] Open
Abstract
Multicellular organisms depend on oxygen-carrying proteins to transport oxygen throughout the body; therefore, proteins such as hemoglobins (Hbs), hemocyanins, and hemerythrins are essential for maintenance of tissues and cellular respiration. Vertebrate Hbs are among the most extensively studied proteins; however, much less is known about invertebrate Hbs. Recent studies of hemocyanins and hemerythrins have demonstrated that they have much wider distributions than previously thought, suggesting that oxygen-binding protein diversity is underestimated across metazoans. Hexagonal bilayer hemoglobin (HBL-Hb), a blood pigment found exclusively in annelids, is a polymer comprised up to 144 extracellular globins and 36 linker chains. To further understand the evolutionary history of this protein complex, we explored the diversity of linkers and extracellular globins from HBL-Hbs using in silico approaches on 319 metazoan and one choanoflagellate transcriptomes. We found 559 extracellular globin and 414 linker genes transcribed in 171 species from ten animal phyla with new records in Echinodermata, Hemichordata, Brachiopoda, Mollusca, Nemertea, Bryozoa, Phoronida, Platyhelminthes, and Priapulida. Contrary to previous suggestions that linkers and extracellular globins emerged in the annelid ancestor, our findings indicate that they have putatively emerged before the protostome-deuterostome split. For the first time, we unveiled the comprehensive evolutionary history of metazoan HBL-Hb components, which consists of multiple episodes of gene gains and losses. Moreover, because our study design surveyed linkers and extracellular globins independently, we were able to cross-validate our results, significantly reducing the rate of false positives. We confirmed that the distribution of HBL-Hb components has until now been underestimated among animals.
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Affiliation(s)
- Flávia A Belato
- Laboratório de Biologia Evolutiva Teórica e Aplicada, Departamento de Genética, Universidade Federal do Rio de Janeiro, RJ, Brazil
| | - Carlos G Schrago
- Laboratório de Biologia Evolutiva Teórica e Aplicada, Departamento de Genética, Universidade Federal do Rio de Janeiro, RJ, Brazil
| | - Christopher J Coates
- Department of Biosciences, College of Science, Swansea University, United Kingdom
| | - Kenneth M Halanych
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University
| | - Elisa M Costa-Paiva
- Laboratório de Biologia Evolutiva Teórica e Aplicada, Departamento de Genética, Universidade Federal do Rio de Janeiro, RJ, Brazil
- Departamento de Zoologia, Instituto Biociências, Universidade de São Paulo, SP, Brazil
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Le Pape F, Richard G, Porchet E, Sourice S, Dubrana F, Férec C, Polard V, Pace R, Weiss P, Zal F, Delépine P, Leize E. Adhesion, proliferation and osteogenic differentiation of human MSCs cultured under perfusion with a marine oxygen carrier on an allogenic bone substitute. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2017; 46:95-107. [DOI: 10.1080/21691401.2017.1365724] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Fiona Le Pape
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
- HEMARINA SA, Aeropole Center, Biotechnopole, Morlaix, France
| | - Gaëlle Richard
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
- French Blood Service-Brittany, Brest, France
| | - Emmanuelle Porchet
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
| | - Sophie Sourice
- INSERM Research Unit 791, Center for Osteoarticular and Dental Tissue Engineering, University of Nantes, Nantes, France
- Regional University Hospital Center of Nantes, Nantes, France
| | | | - Claude Férec
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
- French Blood Service-Brittany, Brest, France
- Regional University Hospital Center, Brest, France
| | - Valérie Polard
- HEMARINA SA, Aeropole Center, Biotechnopole, Morlaix, France
| | - Richard Pace
- INSERM Research Unit 791, Center for Osteoarticular and Dental Tissue Engineering, University of Nantes, Nantes, France
| | - Pierre Weiss
- INSERM Research Unit 791, Center for Osteoarticular and Dental Tissue Engineering, University of Nantes, Nantes, France
| | - Franck Zal
- HEMARINA SA, Aeropole Center, Biotechnopole, Morlaix, France
| | - Pascal Delépine
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
- French Blood Service-Brittany, Brest, France
| | - Elisabeth Leize
- Functional Genetics Department, INSERM Research Unit 1078, University of Western Brittany, European Brittany University, Brest, France
- Prosthesis Department, Research and Formation Unit of Odontology, Regional University Hospital Center of Brest, Brest, France
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Wippler J, Kleiner M, Lott C, Gruhl A, Abraham PE, Giannone RJ, Young JC, Hettich RL, Dubilier N. Transcriptomic and proteomic insights into innate immunity and adaptations to a symbiotic lifestyle in the gutless marine worm Olavius algarvensis. BMC Genomics 2016; 17:942. [PMID: 27871231 PMCID: PMC5117596 DOI: 10.1186/s12864-016-3293-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 11/15/2016] [Indexed: 02/07/2023] Open
Abstract
Background The gutless marine worm Olavius algarvensis has a completely reduced digestive and excretory system, and lives in an obligate nutritional symbiosis with bacterial symbionts. While considerable knowledge has been gained of the symbionts, the host has remained largely unstudied. Here, we generated transcriptomes and proteomes of O. algarvensis to better understand how this annelid worm gains nutrition from its symbionts, how it adapted physiologically to a symbiotic lifestyle, and how its innate immune system recognizes and responds to its symbiotic microbiota. Results Key adaptations to the symbiosis include (i) the expression of gut-specific digestive enzymes despite the absence of a gut, most likely for the digestion of symbionts in the host's epidermal cells; (ii) a modified hemoglobin that may bind hydrogen sulfide produced by two of the worm’s symbionts; and (iii) the expression of a very abundant protein for oxygen storage, hemerythrin, that could provide oxygen to the symbionts and the host under anoxic conditions. Additionally, we identified a large repertoire of proteins involved in interactions between the worm's innate immune system and its symbiotic microbiota, such as peptidoglycan recognition proteins, lectins, fibrinogen-related proteins, Toll and scavenger receptors, and antimicrobial proteins. Conclusions We show how this worm, over the course of evolutionary time, has modified widely-used proteins and changed their expression patterns in adaptation to its symbiotic lifestyle and describe expressed components of the innate immune system in a marine oligochaete. Our results provide further support for the recent realization that animals have evolved within the context of their associations with microbes and that their adaptive responses to symbiotic microbiota have led to biological innovations. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3293-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Juliane Wippler
- Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany. .,Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany.
| | - Manuel Kleiner
- Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany. .,Energy Bioengineering and Geomicrobiology Research Group, University of Calgary, Calgary, T2N 1N4, AB, Canada.
| | - Christian Lott
- Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany.,HYDRA Institute for Marine Sciences, Elba Field Station, Via del Forno 80, 57034, Campo nell' Elba, (LI), Italy
| | - Alexander Gruhl
- Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
| | - Paul E Abraham
- Oak Ridge National Laboratory, Chemical Sciences Division, Oak Ridge, Tennessee, 1 Bethel Valley Rd, Oak Ridge, TN, 37831, USA
| | - Richard J Giannone
- Oak Ridge National Laboratory, Chemical Sciences Division, Oak Ridge, Tennessee, 1 Bethel Valley Rd, Oak Ridge, TN, 37831, USA
| | - Jacque C Young
- Oak Ridge National Laboratory, Chemical Sciences Division, Oak Ridge, Tennessee, 1 Bethel Valley Rd, Oak Ridge, TN, 37831, USA.,Present Address: Saul Ewing LLP, 1500 Market Street, 37th Floor, Philadelphia, PA, 19102-2186, USA
| | - Robert L Hettich
- Oak Ridge National Laboratory, Chemical Sciences Division, Oak Ridge, Tennessee, 1 Bethel Valley Rd, Oak Ridge, TN, 37831, USA
| | - Nicole Dubilier
- Symbiosis Department, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
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Le Pape F, Bossard M, Dutheil D, Rousselot M, Polard V, Férec C, Leize E, Delépine P, Zal F. Advancement in recombinant protein production using a marine oxygen carrier to enhance oxygen transfer in a CHO-S cell line. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2015; 43:186-95. [DOI: 10.3109/21691401.2015.1029632] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Neave MJ, Streten-Joyce C, Nouwens AS, Glasby CJ, McGuinness KA, Parry DL, Gibb KS. The transcriptome and proteome are altered in marine polychaetes (Annelida) exposed to elevated metal levels. J Proteomics 2012; 75:2721-35. [PMID: 22484056 DOI: 10.1016/j.jprot.2012.03.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 03/13/2012] [Accepted: 03/20/2012] [Indexed: 01/09/2023]
Abstract
Polychaetes are often used in toxicological studies to understand mechanisms of resistance and for biomarker detection, however, we know of only a few genetic pathways involved in resistance. We found the marine polychaete Ophelina sp.1 (Opheliidae) in sediment containing high copper levels and investigated this phenomenon by measuring metal accumulation in the worms and changes in gene and protein expression. We sequenced the transcriptome of Ophelina sp.1 from both the impacted and reference sediments using 454-sequencing and analysed their proteomes using differential in gel electrophoresis (DIGE). We used the sequenced transcriptome to guide protein identification. Transcripts coding for the copper chaperone, Atox1, were up-regulated in the worms inhabiting the high copper sediment. In addition, genes coding for respiratory proteins, detoxification proteins and cytoskeletal proteins were significantly altered in metal-exposed worms; many of these changes were also detected in the proteome. This dual approach has provided a better understanding of heavy metal resistance in polychaetes and we now have a wider range of suitable indicator genes and proteins for future biomarker development.
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Thuillier R, Dutheil D, Trieu MTN, Mallet V, Allain G, Rousselot M, Denizot M, Goujon JM, Zal F, Hauet T. Supplementation with a new therapeutic oxygen carrier reduces chronic fibrosis and organ dysfunction in kidney static preservation. Am J Transplant 2011; 11:1845-60. [PMID: 21875432 DOI: 10.1111/j.1600-6143.2011.03614.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Static preservation is currently the most widely used organ preservation strategy; however, decreased donor organ quality is impacting outcome negatively. M101 is an O₂ carrier with high-oxygen affinity and the capacity to function at low temperatures. We tested the benefits of M101 both in vitro, on cold preserved LLC-PK1, as well as in vivo, in a large white pig kidney autotransplantation model. In vitro, M101 supplementation reduced cold storage-induced cell death. In vivo, early follow-up demonstrated superiority of M101-supplemented solutions, lowering the peak of serum creatinine and increasing the speed of function recovery. On the longer term, supplementation with M101 reduced kidney inflammation levels and maintained structural integrity, particularly with University of Wisconsin (UW). At the end of the 3-month follow-up, M101 supplementation proved beneficial in terms of survival and function, as well as slowing the advance of interstitial fibrosis. We show that addition of M101 to classic organ preservation protocols with UW and Histidine-Tryptophane-Ketoglutarate, the two most widely used solutions worldwide in kidney preservation, provides significant benefits to grafts, both on early function recovery and outcome. Simple supplementation of the solution with M101 is easily translatable to the clinic and shows promises in terms of outcome.
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Affiliation(s)
- R Thuillier
- Inserm U927, Faculté de Médecine et Pharmacie, University of Poitiers, Poitiers, F86000, France
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Harnois T, Rousselot M, Rogniaux H, Zal F. High-level Production of RecombinantArenicola MarinaGlobin Chains inEscherichia Coli:A New Generation of Blood Substitute. ACTA ACUST UNITED AC 2009; 37:106-16. [DOI: 10.1080/10731190902908445] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Numoto N, Nakagawa T, Kita A, Sasayama Y, Fukumori Y, Miki K. Structure of the partially unliganded met state of 400 kDa hemoglobin: Insights into ligand-induced structural changes of giant hemoglobins. Proteins 2008; 73:113-25. [DOI: 10.1002/prot.22040] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Royer WE, Omartian MN, Knapp JE. Low Resolution Crystal Structure of Arenicola Erythrocruorin: Influence of Coiled Coils on the Architecture of a Megadalton Respiratory Protein. J Mol Biol 2007; 365:226-36. [PMID: 17084861 PMCID: PMC1847385 DOI: 10.1016/j.jmb.2006.10.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/27/2006] [Accepted: 10/05/2006] [Indexed: 11/17/2022]
Abstract
Annelid erythrocruorins are extracellular respiratory complexes assembled from 180 subunits into hexagonal bilayers. Cryo-electron microscopic experiments have identified two different architectural classes. In one, designated type I, the vertices of the two hexagonal layers are partially staggered, with one hexagonal layer rotated by about 16 degrees relative to the other layer, whereas in the other class, termed type II, the vertices are essentially eclipsed. We report here the first crystal structure of a type II erythrocruorin, that from Arenicola marina, at 6.2 A resolution. The structure reveals the presence of long continuous triple-stranded coiled-coil "spokes" projecting towards the molecular center from each one-twelfth unit; interdigitation of these spokes provides the only contacts between the two hexagonal layers of the complex. This arrangement contrasts with that of a type I erythrocruorin from Lumbricus terrestris in which the spokes are broken into two triple-stranded coiled coils with a disjointed connection. The disjointed connection allows formation of a more compact structure in the type I architecture, with the two hexagonal layers closer together and additional extensive contacts between the layers. Comparison of sequences of the coiled-coil regions of various linker subunits shows that the linker subunits from type II erythrocruorins possess continuous heptad repeats, whereas a sequence gap places these repeats out of register in the type I linker subunits, consistent with a disjointed coiled-coil arrangement.
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Affiliation(s)
- William E Royer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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