title: Mistletoe lectin binds to multidrug resistance-associated protein MRP5.
abstract: BACKGROUND
  Mistletoe lectins (MLs) are the active components of aqueous mistletoe extracts widely used in complementary cancer therapy, however, it is not clear if they bind to carbohydrate residues only or whether they interact with proteins as well. Protein-protein interactions do not seem unlikely as MLs act at very low molar concentrations usually observed with peptide-peptide interactions only and not seen with lectin-sugar interactions.
  
  
  METHODS
  In order to detect protein-protein interactions a random peptide library was screened for the ability to bind to MLs.
  
  
  RESULTS
  MLs bound to peptides showing homologies to multidrug resistance-associated protein 5 (MRP5). However, the MLs only slightly modified the MRP5 efflux pump, while periodate treatment to inhibit cell membrane binding via glycan completely abolished the ML-I binding sites in MRP5 overexpressing cells.
  
  
  CONCLUSIONS
  The protein sequence is not important for ML-I binding, indicating that the biological activity of MLs can most likely be attributed to the sugar chains.
authors.affiliation: Department of Anatomy II: Experimental Morphology, University Hospital Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany. nnehmann@uke.unihamburg.de
authors.forename: Nina
authors.initials: N
authors.lastname: Nehmann
authors.forename: Ulrika M
authors.initials: UM
authors.lastname: Schade
authors.forename: Uwe
authors.initials: U
authors.lastname: Pfüller
authors.forename: Melitta
authors.initials: M
authors.lastname: Schachner
authors.forename: Udo
authors.initials: U
authors.lastname: Schumacher
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D037102:Lectins / Q000378:metabolism*; D014784:Mistletoe / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*; D019151:Peptide Library; D010504:Periodic Acid / Q000494:pharmacology; D011134:Polysaccharides / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D037102:Lectins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D019151:Peptide Library; D010504:Periodic Acid; D011134:Polysaccharides; C120809:ABCC5 protein, human; C009288:metaperiodate