title: Crystal structure of kiwellin, a major cell-wall protein from kiwifruit.
abstract: Kiwellin is a cysteine-rich, cell wall-associated protein with no known structural homologues. It is one of the most abundant proteins in kiwifruit (Actinidia spp.), and has been shown to be recognised by IgE of some patients allergic to kiwifruit. Cleavage of kiwellin into an N-terminal 4 kDa peptide called kissper and a core domain called KiTH is mediated by actinidin in vitro, and isolation of the kissper peptide from green-fleshed kiwifruit extracts suggested it may result from in vivo processing of kiwellin. In solution, kissper is highly flexible and displays pore-forming activity in synthetic lipid-bilayers. We present here the 2.05 Å resolution crystal structure of full-length kiwellin, purified from its native source, Actinidia chinensis (gold-fleshed kiwifruit). The structure confirms the modularity of the protein and the intrinsic flexibility of kissper and reveals that KiTH harbours a double-psi β-barrel fold hooked to an N-terminal β hairpin. Comparisons with structurally-related proteins suggest that a deep gorge located at the protein surface forms a binding site for endogenous ligands.
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand. Electronic address: cyril.hamiaux@plantandfood.co.nz.
authors.forename: Cyril
authors.initials: C
authors.lastname: Hamiaux
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand.
authors.forename: Ratnasiri
authors.initials: R
authors.lastname: Maddumage
authors.affiliation: School of Biological Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Middleditch
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand.
authors.forename: Roneel
authors.initials: R
authors.lastname: Prakash
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 11600, Palmerston North 4442, New Zealand.
authors.forename: David A
authors.initials: DA
authors.lastname: Brummell
authors.affiliation: School of Biological Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Edward N
authors.initials: EN
authors.lastname: Baker
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand.
authors.forename: Ross G
authors.initials: RG
authors.lastname: Atkinson
mesh_terms: D029042:Actinidia / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D002686:Chitin / Q000378:metabolism; D018360:Crystallography, X-Ray; D005638:Fruit / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D052179:Antigens, Plant; D009844:Oligosaccharides; D010940:Plant Proteins; D011134:Polysaccharides; C507612:kiwellin protein, Actinidia chinensis; D002686:Chitin
keywords: Double-psi β barrel; Kiwellin; Plant protein