Overview of the Structure–Function Relationships of Mannose-Specific Lectins from Plants, Algae

49 Pages·2017·5.52 MB·English

International Journal o f
Molecular Sciences
Review
Overview of the Structure–Function Relationships of
Mannose-Specific Lectins from Plants, Algae
and Fungi
AnnickBarre1,YvesBourne2,ElsJ.M.VanDamme3 andPierreRougé1,*
1 UMR152PharmaDev,InstitutdeRechercheetDéveloppement,FacultédePharmacie,UniversitéPaul
Sabatier,35ChemindesMaraîchers,31062Toulouse,France;[email protected]
2 CentreNationaldelaRechercheScientifique,Aix-MarseilleUniv,ArchitectureetFonctiondes
MacromoléculesBiologiques,163AvenuedeLuminy,13288Marseille,France;
[email protected]
3 DepartmentofBiotechnology,FacultyofBioscienceEngineering,GhentUniversity,Coupurelinks653,
B-9000Ghent,Belgium;[email protected]
* Correspondence:[email protected];Tel.:[phone]
(cid:1)(cid:2)(cid:3)(cid:1)(cid:4)(cid:5)(cid:6)(cid:7)(cid:8)(cid:1)
(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:7)
Received:11December2018;Accepted:31December2018;Published:10January2019
Abstract: To date, a number of mannose-binding lectins have been isolated and characterized
from plants and fungi. These proteins are composed of different structural scaffold structures
which harbor a single or multiple carbohydrate-binding sites involved in the specific recognition
of mannose-containing glycans. Generally, the mannose-binding site consists of a small, central,
carbohydrate-bindingpocketresponsibleforthe“broadsugar-bindingspecificity”towardasingle
mannose molecule, surrounded by a more extended binding area responsible for the specific
recognition of larger mannose-containing N-glycan chains. Accordingly, the mannose-binding
specificityoftheso-calledmannose-bindinglectinstowardscomplexmannose-containingN-glycans
depends largely on the topography of their mannose-binding site(s). This structure–function
relationship introduces a high degree of specificity in the apparently homogeneous group of
mannose-binding lectins, with respect to the specific recognition of high-mannose and complex
N-glycans. Because of the high specificity towards mannose these lectins are valuable tools for
decipheringandcharacterizingthecomplexmannose-containingglycansthatdecoratebothnormal
and transformed cells, e.g., the altered high-mannose N-glycans that often occur at the surface of
variouscancercells.
Keywords: lectin;plant;fungi;mannose-bindingspecificity;structure;function;useastools
1. Introduction
Protein-carbohydrate interactions are part of the most efficient signaling pathways occurring
inside living organisms or between living organisms and their environment. Lectins or
Carbohydrate-BindingAgents(CBAs)areproteinsthathavespecializedinthespecificrecognitionof
carbohydratesduringtheevolutionofalllivingorganisms. Thelargefamilyofcarbohydrate-binding
proteinscontainsalargevarietyofcarbohydrate-bindingdomains(CBDs),eachwithoneormore
carbohydrate-binding sites (CBSs) which specifically recognize simple or more complex sugars.
Dependingonthelectin,thecarbohydrate-bindingdomainsbelongtodistinctstructuralscaffolds
usuallyorganizedinhomo-orhetero-dimericortetramericstructures[1]. Accordingtothenatureand
theorganizationoftheirdomains,plantandfungallectinshavebeenclassifiedintwogroupsoflectins,
(1)lectinsexclusivelycomposedofcarbohydrate-bindingdomainsand(2)chimerolectinscomposed
ofacarbohydrate-bindingdomainlinkedtoanotherdomain(s)devoidofanycarbohydrate-binding
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properties[1]. Withrespecttotheirbindingproperties,plantandfungallectinscanbesubdivided
in different groups, such as for example Man-specific lectins, Gal/GalNAc-specific lectins, and
Fuc-specificlectins[2]. However,thebindingoflectinstowardssimplesugarsisprobablynotreally
relevant. ItismorerealistictoassumethatlectinswillinteractwiththemorecomplexN-glycanchains
thatdecoratethecellsurfaceofalllivingorganisms[3].Inaddition,theideahasprogressivelyemerged
that, besides lectins which are abundantly distributed in storage tissues like seeds and bulbs and
playadefensive/protectiverole,otherlessabundantlectinsparticipateinmorediscretecarbohydrate
recognitionprocessesequallynecessaryfortheproperfunctioningofthelivingorganisms[4]. Inthis
respect,thediscoveryofNictaba,alectinlocalizedinthenucleusoftobacco(Nicotianatabacum)cells,
representsamilestoneinourvisionofthefunctiondevotedtoplantandfungallectinsinvivo[5].
Owing to the huge amount of structural and functional data that have been accumulated for
several decades these carbohydrate-binding proteins from plants and fungi have become a tool
to decipher the structure–function relationships inherently associated to protein macromolecules.
In this respect, lectins involved in the specific recognition of mannosyl residues, the so-called
mannose-binding lectins, represent an important group of functional proteins taking into account
thewidespreaddistributionofmannose-containingN-glycansoftheN-acetyllactosaminetypeand
high-mannosetype. Thepresentreviewaimstopresentanexhaustiveoverviewthatsummarizes
allpublishedinformationsrelatedtothestructure–functionrelationshipsofmannose-specificlectins
from plants and fungi, and their possible applications as analytical and therapeutic tools for
biomedicalresearch.
2. DiversityofMannose-BindingLectinsinHigherPlants
Todate,lectinswithamannosyl-bindingspecificityhavebeenidentifiedinmanydifferentplant
families,includingmonocotyledonousaswellasdicotyledonousspecies(Table1).Amongthemonocot
families,researchhasfocusedontheLiliaceaeandAmaryllidaceae[6],whereastheFabaceaefamily
occupiesapredominantpositioninthedicotgroup[6]. FollowingtothepioneeringworkofAgrawal
& Goldstein [7], who reported that concanavalin A (Con A), the lectin from Jack bean (Canavalia
ensiformis)seeds,waseasilyretainedbysimplefiltrationthroughacolumncontainingcross-linked
dextrangel(Sephadex,Pharmacia)andsubsequentdesorbtionbytheadditionofglucoseormannose
totheelutingbuffer,bothConAandmanyothermannose-specificlectins(Table1)wereeasilypurified
usingasingleaffinitychromatographystep. Mannose-specificlectinswerealsosuccessfullyisolated
fromdifferentalgae,mushroomsandlowerplantspecies[8]. Moreover,somemannose-specificlectins
fromredalgaespecificallyrecognizethecore(α1-6)-fucosylatedN-glycansofcancercellsandcanbe
usedasbiomarkersforthedetectionofcancerglycoforms[9]. Inthisrespect,theyresembleLcAfrom
Lensculinaris,PsAfromPisumsativumandLoL-IfromLathyrusochrus,whichshowstrongbindingto
core-fucosylatedmono-andbi-antennaryN-glycans[10,11].
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Table1.Overviewofplant,algaeandfungilectinswithamannosyl-bindingspecificity(β-sandwich:βs,β-prism:βp,n.d.:notdetermined).
Plant,Alga,MushroomFamily Plant,Alga,MushroomSpecies Lectin StructuralScaffold Oligomer Ref.
Pteridophyta Phlebodiumaureum PAL βbarrel 2 [12]
LectinI n.d. 10
Araucariabrasiliensis [13]
Lectin2 n.d. 6
Gymnosperms
Gingkobiloba Gnk2 αβ 1 [14]
Cycasrevoluta CRLL β-prism 2 [15,16]
Bowringiamildbraedii BMA β-sandwich 2/4 [17]
Cajanuscajan CcL βs 2 [18]
Camptosemapedicellatum CPL βs 4 [19]
Canavaliaboliviana ConBo βs 4 [20]
Canavaliabonariensis CaBo βs 4 [21]
Canavaliabrasiliensis ConBr βs 4 [22]
Canavaliaensiformis ConA βs 4 [23]
Canavaliagladiata CGL βs 4 [24]
Canavaliagrandiflora ConGF βs 4 [25]
Canavaliamaritima ConM βs 4 [26]
Canavaliavirosa ConV βs 4 [27]
Centrolobiummicrochaete CML βs 4 [28]
Centrolobiumtomentosum CTL βs 4 [29]
Cladrastislutea CLAI,II βs 4 [30]
Fabaceae Cratyliafloribunda CFL βs 2/4 [31]
Cratyliamollis CRAMOLL βs 2/4 [32]
Cymbosemaroseum CRLI βs 4 [33]
Diocleagrandiflora DGL βs 4 [34,35]
Diocleaguianensis Dguia βs 4 [36]
Dioclealasiocarpa DLL βs 4 [37]
Dioclealasiophylla DlyL βs 4 [38]
Diocleareflexa DrfL βs 4 [39]
Dioclearostrata DRL βs 4 [40]
Diocleasclerocarpa DSL βs 4 [41]
Diocleaviolacea DVL βs 4 [42]
Diocleavirgata DvirL βs 4 [43]
Diocleawilsonii DwL βs 4 [44]
Lathyrusaphaca LaphL βs 2 [45]
Lathyrusarticulatus LarL βs 2 [45]
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Table1.Cont.
Plant,Alga,MushroomFamily Plant,Alga,MushroomSpecies Lectin StructuralScaffold Oligomer Ref.
Lathyruscicera LcL βs 2 [45]
Lathyrushirsutus LhL βs 2 [46]
Lathyrusnissolia LnL βs 1 [47]
Lathyrusochrus LoL βs 2 [48]
Lathyrusodoratus LodL βs 2 [49]
Lathyrussativus LsL βs 2 [50]
Lathyrussphaericus LsphL βs 1 [51]
Lathyussylvestris LsiL βs 2 [52]
Lathyrustingitanus LtL βs 2 [46]
Lensculinaris LcA βs 2 [53]
Millettiadielsiana MDL βs 2 [54]
Onobrychisviciifolia βs n.d. [55]
Pisumarvense PAL βs 2 [56]
Pisumsativum PsA βs 2 [57]
Pterocarpusangolensis PAL βs 2 [58]
Sophoraflavescens SFL βs 2 [59]
Trigonellafoenumgraecum βs n.d. [60]
Viciacracca βs 2 [61]
Viciaervilia βs 4 [62]
Viciafaba VfA βs 2 [63]
Viciasativa βs 2 [64]
Parkiabiglobosa PBL βs 2 [65]
Mimosaceae
Parkiaplatycephala PPL βs 2 [66]
Platypodiumelegans nPELa βs 2 [67]
Dalbergieae
Platymisciumfloribundum PFL βs 2 [68]
Fagaceae Castaneacrenata CCA βs 6/8 [69]
Artocarpusheterophyllus ArtinM β-prism 4 [70,71]
Artocarpusincisa Frutapin βp 4 [72]
Artocarpusinteger CMB βp 4 [73,74]
Moraceae artocarpin βp 4 [75,76]
Artocarpusintegrifolia
jacalin βp 4 [77,78]
Artocarpuslakoocha artocarpin βp 4 [79]
Morusnigra Moniga-M βp 4 [80]
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Table1.Cont.
Plant,Alga,MushroomFamily Plant,Alga,MushroomSpecies Lectin StructuralScaffold Oligomer Ref.
Asteraceae Helianthustuberosus Heltuba βp 8 [81]
Brassicaceae Arabidopsisthaliana PP2-A1 βp n.d. [82]
Ranonculaceae Clematismontana CML βp 2 [83]
Aloeae Aloearborescens ALOE βp 4 [84]
Arisaemalobatum ALA n.d. 2+2 [85]
Arisaemaheterophyllum AHA βp n.d [86]
Arummaculatum AMA βp 2+2 [87]
Colocasiaesculenta CEA,tarin βp 2+2 [88]
Dieffenbachiasequina βp 2+2 [87]
Araceae Lysichitoncamtschatcensis βp 2+2 [89]
Pinelliaternata PTA βp 2+2 [90]
Remusatiavivipara RVL βp 2+2 [91]
Typhoniumdivaricatum TDL βp 2+2 [92]
Xanthosomasagittifolium XSL βp 2+2 [93]
Zantedeschiaaethiopica ZAA βp n.d. [94]
Ophiopogonjaponicus OJL βp n.d. [95]
Asparagaceae Polygonatumcyrtonema PCL βp 4 [96]
Polygonatummultiflorum PMA βp 4 [97]
Polygonatumodoratum POL βp 4 [98]
Convolvulaceae Calystegiasepium Calsepa βp 2 [99]
Ipomoeabatatas ipomoelin βp 4 [100]
Alliumaltaicum AALTA βp 2 [101]
Alliumascalonicum AAA βp 2 [102]
Alliumcepa ACA βp 2 [103]
Alliaceae Alliumporrum APA βp 2 [103]
Alliumsativum ASA-I/II βp 2 [104]
Alliumtuberosum ATA βp 2 [105]
Alliumursinum AUA-I/II βp 2 [106]
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Table1.Cont.
Plant,Alga,MushroomFamily Plant,Alga,MushroomSpecies Lectin StructuralScaffold Oligomer Ref.
Amaryllisvittata AVA βp n.d. [107]
Cliviaminiata CMA βs 2 [108]
Crinumasiaticum CAA βp n.d. [109]
Galanthusnivalis GNA βp 4 [110]
Hippeastrumhybrid HHA βp 2 [111]
Amaryllidaceae
Leucojumvernum LVL βp n.d. [112]
Zephyranthescandida ZCA βp 4 [113]
Zephyranthesgrandiflora ZGA βp 4 [114]
Lycorisaurea LAA βp 2 [115]
Lycorisradiata LRA βp 2 [116]
Dioscoreabatatas DB1 βp 1 [117]
Dioscoreaceae
Dioscoreabulbifera DBL βp 1 [118]
Crocussativus CSL βp n.d. [119,120]
Iridaceae
Crocusvernus CVA βp 4 [121]
Aspidistraelatior AEL n.d. 2 [122]
Narcissuspseudonarcissus NPA βp 2,4 [111]
Narcissustazetta NTL βp 2 [123]
Liliaceae
Narcissustortifolius NTA βp n.d. [124]
TxLCI βp 4
Tulipahybrid [125]
TL-MII βp 2
Smilacaceae Smilaxglabra SGM2 βp 3 [126]
Hyacintheae Scillacampanulata SCAman βp 2 [127]
Musaacuminata BanLec βp 2 [128]
Musaceae
Musaparadisiaca βp 2 [129]
Pandanaceae Pandanusamaryllifolius pandanin βp n.d. [130]
Cymbidiumhybridum CHA βp 2 [131]
Dendrobiumofficinale DOA2 βp n.d. [132]
Epipactishelleborine EHMBP βp 2 [131]
Orchidaceae
Gastrodiaelata gastrodianine βp 2 [133]
Liparisnoversa LNL βp 2 [95]
Listeraovata LNL βp 2 [131]
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Table1.Cont.
Plant,Alga,MushroomFamily Plant,Alga,MushroomSpecies Lectin StructuralScaffold Oligomer Ref.
Poaceae Oryzasativa Orysata βp 2 [134]
Bryothamnionseaforthii BSL n.d. 1 [135]
Bryothamniontriquetrum BTL n.d. 1,2 [136]
Euchemadenticulatum EDA n.d. 1 [137]
Eucheumaserra ESA n.d. 1 [138]
Griffithsiasp. griffithsin n.d. 2 [139,140]
Redalgae
Hypneacervicornis HCA n.d. 1 [141]
Hypneajaponica HJA n.d. 1 [9]
Hypneamusciformis HMA n.d. 1 [142]
Kappaphycusalvarezii KAA-2 n.d. 1 [143]
Kappaphycusstriatum KSA n.d. 1 [144]
Boodleacoacta BCA β-prism 1 [145]
Greenalgae
Halimedarenschii HRL40-1/2 n.d. 4 [146]
Hydnangiaceae Laccariabicolor tectonin2 β-propeller n.d. [147,148]
Trichocomaceae Penicilliumchrysogenum PeCL n.d. n.d. [149]
Saccharomycescerevisiae Flo5A β-sandwich 2 [150]
Saccharomycetaceae
Saccharomycespasteurianus Flo1p βs 4 [151]
Schizosaccharo-mycetaceae Schizosaccharomycespombe glucosidase βs 2 [152]
Hygrophoraceae Hygrophorusrussula HRL n.d. 4 [153]
Marasmiaceae Marasmusoreades MOA β-prism 2 [154]
Pteridaceae Ceratopterisrichardii cyanovirin CVN-fold 1 [155]
Sordariaceae Neurosporacrassa cyanovirin CVN-fold 1 [155]
Tuberaceae Tuberborchii cyanovirin CVN-fold 1 [155]
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3. StructuralOrganizationofthePlant,AlgalandFungalMannose-BindingLectins
3.1. StructureofMannose-SpecificPlantLectins
Mannose-specificlectinsfromplantsessentiallybelongtothreedistinctstructuralscaffoldsthat
assembleindifferentwaystogeneratemorecomplexoligomericstructures:
3.1.1. Theβ-SandwichFold
Thejellyrollscaffoldoccurringinlegumelectins(Fabaceae)consistsofeitherasingleortwo
polypeptidechains. Intwo-chainlectins,thelight(α)andheavy(β)chainsmadeofsixandseven
strands of antiparallel β-sheet, respectively, non-covalently associate in a β-sandwich protomer
(Figure 1A). Protomers associate by non covalent bonds to give the homodimeric lectins of the
Vicieaetribe,e.g.,pealectin(PisumsativumagglutininPsA)[57],lentillectin(Lensculinarisagglutinin
LcA)[156],yellowvetchlectin(LathyrusochruslectinLol)[48](Figure1B),andthefababeanlectin
(ViciafabaagglutininVfAorfavin)[63](Figure1B).Incontrast,theMan-specificlectinfromLathyrus
sphaericusconsistsofanuncleavedsinglechainprotomer[51]. Thesingle-chainprotomersassociate
intohomotetramers. Examplesarethemannose-bindinglectinscharacterizedinthetribesBaphieae
(Bowringia mildbraedii agglutinin BMA) [17], Dalbergieae (Centrolobium tomentosum lectin CTL [29],
PterocarpusangolensislectinPAL[58]),Diocleae(ConA[23,157](Figure1C),CymbosemaroseumCRL[33],
Dioclea grandiflora lectin Con GF [25], and other Dioclea sp. lectins). Dimeric lectins such as PsA,
possess two identical mannose-binding sites whereas tetrameric lectins like Con A, exhibit four
mannose-bindingsites. Gal/GalNAc-specificlectinsfromotherlegumetribessuchasthesoybean
agglutininSBA(Glycinemax)fromtheGlycinaetribe(PDBcode1SBF)[158],thepeanutagglutinin
PNA(Arachishypogaea)fromtheAeschynomeneae(PDBcode2PEL)[159],thecoraltreelectinEcorL
(Erythrina corallodendron) from the Erythrinae tribe (PDB code 1AXY) [160], and the kidney bean
leucoagglutininPHA-L(PDBcode1FAT)[161]anderythroagglutininPHA-E(PDBcode3WCR)[162],
(Phaseolusvulgaris)belongingtothePhaseolaetribe,allstrikinglyresembleConAandotherDiocleae
lectinsbutdifferinthetopologicalorganizationforthesingle-chainprotomersthatconstitutethelectin.
3.1.2. Theβ-PrismIFold
Theβ-prismIscaffoldservesasabuildingblockforthemannose-bindinglectinsinseedsofthe
Moraceaesuchasartocarpin,thelectinfromtheJackfruit(Artocarpusintegrifolia)seedswhichserves
asaprototypeforthisgroup[163]. Theβ-prismIscaffoldconsistsofthreebundlesoffourantiparallel
β-strandsformingthreeGreekkeys1,2and3,arrangedintoaβ-prismstructurealongalongitudinal
axis (Figure 1D). Depending on the lectins, a posttranslational proteolytic cleavage between the
β-strandsβ1andβ2ofGreekkey1occursduringseedripening,toliberatethelightα-chainwitha
terminalGly1residueexhibitingafreeH N-group,andtheheavyβ-chaincomprisingtherestofthe
2
β-prismstructure. ThisproteolyticcleavageoccursintheGal/GalNAc-specifichomotetramericlectins
ofMoraceae,suchasjacalin(Figure1E)(PDBcode1JAC)[164],theMPAlectinfromOsageorange
(Maclurapomifera)seeds(PDBcode1JOT)[165],andtheGal/GalNAc-specificlectinMorniga-Gfrom
thebarkofblackberry(Morusnigra)[80]. However,theMan-specificlectinsfromtheMoraceaefamily,
e.g.,artocarpinfromJackfruit[163]andMorniga-Mfromblackberry[166],consistofanuncleaved
single-chainβ-prismpolypeptidechain. Similarly,Heltuba,thelectinfromtheJerusalemartichocke
(Helianthustuberosus),alsoconsistsofasingle-chainβ-prismpolypeptidechainmadeof8β-prisms
non-covalentltyassociatedaroundacentralaxistoformaflattenedstar-shapedarchitecturecomprising
8identicalcarbohydrate-bindingsites(Figure1F)[81].
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Int. J. Mol. Sci. 2019, 20

Figure1.Structuraldiversityofthemannose-bindinglectins.(A).Two-chainlectinprotomerofLathyrus
Figure 1. Structural diversity of the mannose-binding lectins. (A). Two-chain lectin protomer of
ochrus(PDBcode1LOE[48]). Lightchainandheavychainsarecoloredgreenandred,respectively.
Lathyrus ochrus (PDB code 1LOE [48]). Light chain and heavy chains are colored green and red,
(B). Homodimeric organization of the L. ochrus isolectin-I (1LOE). The light and heavy chains of
respectively. (B). Homodimeric organization of the L. ochrus isolectin-I (1LOE). The light and heavy
the dimer are colored differently. (C). Homotetrameric organization of Con A (PDB code 3CNA).
chains of the dimer are colored differently. (C). Homotetrameric organization of Con A (PDB code
Thefoursingle-chainprotomersareshownindifferentcolors.(D).Theβ-prismorganizationofthe
3CNA). The four single-chain protomers are shown in different colors. (D). The β-prism organization
artocarpinprotomerfromArtocarpusintegrifolia(PDBcode1J4S).Thethreebundlesofβ-strandsforming
of the artocarpin protomer from Artocarpus integrifolia (PDB code 1J4S). The three bundles of β-strands
theβ-prismarecoloredgreen, redandorange, respectively. (E).Homotetramericorganizationof
forming the β-prism are colored green, red and orange, respectively. (E). Homotetrameric
artocarpinfromA.integrifolia(1J4U).Theβ-prismprotomersarecoloreddifferently.(F).Homooctameric
organization of artocarpin from A. integrifolia (1J4U). The β-prism protomers are colored differently.
organizationofHeltubafromHelianthustuberosus(1C3M)[81]. Theβ-prismprotomersarecolored
(F). Homooctameric organization of Heltuba from Helianthus tuberosus (1C3M) [81]. The β-prism
differently.(G).Theβ-prismIIorganizationoftheprotomerofGNAfromGalanthusnivalis(PDBcode
protomers are colored differently. (G). The β-prism II organization of the protomer of GNA from
1MSA).(H).Organizationoftheβ-prismIIprotomersintheGNAtetramer(PDBcode1MSA).(I).
Galanthus nivalis (PDB code 1MSA). (H). Organization of the β-prism II protomers in the GNA
HexamericstructureofthetarinlectinfromColocasiaesculenta(PDBcode5T20).Thesixβ-prism-folded
tetramer (PDB code 1MSA). I. Hexameric structure of the tarin lectin from Colocasia esculenta (PDB
protomersarecoloreddifferently.
code 5T20). The six β-prism-folded protomers are colored differently.
3.1.3. Theβ-PrismIIFold
3.1.3. The β-prism II Fold
The β-prism II scaffold was first identified in GNA, the mannose-specific lectin isolated
fromTthhee βb-uprlbissmo IfI ssncoafwfodlrdo wpa(sG failrasnt tihduesntnifiiveadli sin), GaNpAla,n tthes pmeacniensobsee-lospnegciinfigc tleocttihne ismoolanteodco ftrofmam thiley
bAumlbasr ylolifd ascneoaew[d1r1o0p]. T(hGealsacnatfhfoulsd cnoinvasilsist)s, ofat hprelaenbtu nsdpleecsieosf fobuerloβn-gstirnagn dtsoa rrthane gemdoinntoocoatfl aftatemnielyd
Amaryllidaceae [110]. The scaffold consists of three bundles of four β-strands arranged into a
flattened β-prism structure around a central pseudoaxis (Figure 1G). A carbohydrate-binding site
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Int. J. Mol. Sci. 2019, 20
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oktDhear alnecdt itnwsoc o1n4s kisDtao fβh-petreirsomtr seutrbaumneitrss, beu.gil.t, tuhpe fArormacethaee sleycmtimnse [t6ri]c. aUlsaussaollcyia, tailoln thorfetew coar1b2okhDydaraanted-
tbwinod1in4gk sDitaesβ o-pccriusrmrinsgu binu neaitcsh, eβ.-gp.,ritshme Ascraaffcoelade alerec trienasd[i6ly]. fUunsuctaiollny,aal lblutth irne ea cfaewrb olehcytidnrsa, toen-bei onrd tiwngo
sciaterbsoohcycdurraritne-gbiinndienagc hsitβe-sp arriesm apspcaarfefnotldly ainreacrteivaed diluyef tuon pctoiionnt amlubtuattiionn(as)f ienw kelyec rteinsisd,uoense inovroltvweod
cianr btohhey dHr-abtoe-nbdinindgin gofs imtesananreoasep.p aTraernintl yfirnoamct ivCeoldocuaesitao pesociunltenmtau taatsisoenm(sb)leins kienytor eshiodmueoshienxvaomlveerdic
isntrtuhcetuHr-ebso mndaidneg ooff 6m βa-npnriossme. sTcaarfifnolfdrosm [1C68o]lo (cFaisgiaureesc 1uIl)e.n taassemblesintohomohexamericstructures
madeTohfe6 ββ--tprerfisomil ssccaaffffoolldds, [a1n6o8t]h(eFrig βu-rper1isI)m. II scaffold, has been primarily identified in type II
RiboTsohmeeβ-I-ntraecfotiivlastcinagff oPlrdo,teainnost h(RerIPβ-I-Ip),r iisnm amIIasrcaanftfhoilnd,, ah Tas abnetiegnenp-rsipmeacirfiilcy liedcetinnt iffrieodm inamtyarpaentIhI
R(Aibmoasroamnteh-uIns accatuivdaattiunsg) P[1r6o9te],i nasnd(R IiPt -aIIls),o inocacmurasr ainn ththine, satrTesas nitnigdeunc-isbplee clieficctilnesc tcinomfrpoomseadm oafr aEnUthL
((AEmuoanraynmthuuss lceacutidna)t udso)m[16a9in],sa, nsducihta alsso thocec luercstiinnst hfreosmtre rsiscein (dOurcyibzale slaetcitvian)s acnodm AporasebdidoopfsEisU [L17(E0u].o Tnyhme uβs-
ltercetfioni)l dscoamffaoilnds ,csouncshisatss othf esilxe cβt-inhsaifrrpoimnsr aicrera(nOgreydza asraotuivnad)a annd aAprparboidxoimpsaiste[1 t7h0r]e.eT-fhoeldβ -styrmefomilestrcyaf afoxlids,
cloinnkseisdts toof esxixteβn-dheadir ploinospasr rthanatg esdimaurolautned thane athprpereo xloimbeast eotfh are ter-effooldil slyeamf m(Feitgruyraex i2s),. liTnhkee dMtaone-xbtiennddiendg
lsoiotepss athrea tlosicmatuelda tient htheet hsrheaellloowbe sdoepfraetsrseifoonils leoaf ft(hFei gβu-rsetr2a)n.dTsh ebuMt,a un-sbuianldlyin ngosti taelsl abriendloicnagt esditeins tahree
sfhuanlclotiwondael.p ressionsoftheβ-strandsbut,usuallynotallbindingsitesarefunctional.

Figure 2. Three-dimensional models for the EUL domain of EUL-domains of rice lectin Orysata,
sFhiogwurien g2t. hTehβre-ter-edfoimilleonrsgioannaizl amtioondemlsa dfoero tfhteh rEeUebLu dnodmleasionf oanf tEipUaLra-dlloemlβa-isnhse eotfs r(iIc,eII ,leIIcIt)i.n Orysata,
showing the β-trefoill organization made of three bundles of antiparallel β-sheets (I, II, III).
An unexpected four-bladed β-propeller structure was found to occur in a PA albumin from
2
chickpAena u(Cniecexrpaerciteetidn ufmou),r-wbhlaicdhedd iβsp-plaryospaelwleer llstdrouccutumreen wteads hfeomunagdg tlou toincactuinr gina cat ivPiAty2 malobsutmprino bfarbolmy
rcehlaictkedpetao a(Cleiccetrin awriietthinaunmu),n uwshuiaclhh edmisopplaeyxsin afo lwde[l1l 71d]o.cumented hemagglutinating activity most
probably related to a lectin with an unusual hemopexin fold [171].
3.2. StructureofMannose-SpecificAlgalLectins
3.2. Structure of Mannose-Specific Algal Lectins
The mannose-specific lectin griffthsin from the red alga Griffthsia sp., consists of a domain-
swapTphede mdiamnenromsea-sdpeecoiffitcw loecptirno tgormifeftrhesxinh ifbriotimng ththee rβed-p arilsgma GIrfoiflftdh,stiah astpc.,l ocsoenlysisretss eomf bal edsotmoathine-
jsawcaalpinp-eredl adteimdelerc mtinadoerg oafn tizwaoti opnro(tPoDmBerc oedxehi2bGitTinYg) [t1h4e0 β].-Spwrisampp Ii nfgolrde,s uthltast fcrloomsetlhy erepsaermticbilpeast itoon thofe
tjwacoalβin-s-trrealnatdesdo lfeoctnine moroglaencuizleatiinonth (ePcDoBm cpoldetei o2nGoTfYt)h [e1t4h0r]e. eSwfoaupr-psitnragn rdeesdulsths eferotsmfo trhme ipnagrttihceipβa-tpiorins mof
otwftoh eβo-sthtrearnmdso loefc uolne,e amndolveiccuelev eirns at.hAe scoamrepsluelttioonf thofis tshwe atphpreine gf,obuort-hstmraonldeecudl esshienettsh efodrimmienrgc othnes iβst-
opfraiscmo mofp tlheete oβth-perr imsmoleocrugalen, iaznadti ovnic(eF vigeursrae.3 A).s a result of this swapping, both molecules in the dimer
consIinst sopfi tae coofmaphliegthe βn-upmribsemr oofrgcalonnizeadtiaonnd (sFeiqguueren c3e)d. lectinsfromdifferentspeciesofredandgreen
algae,theirthree-dimensionalorganization(s)werepoorlyinvestigatedandstillremainunknown.
Theiraminoacidsequencesreadilydifferfromthatofgriffithsinand,mostprobably,theyalsodiffer
fromgriffithsinbytheirthree-dimensionalstructureandmonomerorganization.