title: Use of a HEHEHE purification tag instead of a hexahistidine tag improves biodistribution of affibody molecules site-specifically labeled with (99m)Tc, (111)In, and (125)I.
abstract: Affibody molecules are a class of small (∼7 kDa) robust scaffold proteins suitable for radionuclide molecular imaging in vivo. The attachment of a hexahistidine (His(6))-tag to the Affibody molecule allows facile purification by immobilized metal ion affinity chromatography (IMAC) but leads to high accumulation of radioactivity in the liver. Earlier, we have demonstrated that replacement of the His(6)-tag with the negatively charged histidine-glutamate-histidine-glutamate-histidine-glutamate (HEHEHE)-tag permits purification of Affibody molecules by IMAC, enables labeling with [(99m)Tc(CO)(3)](+), and provides low hepatic accumulation of radioactivity. In this study, we compared the biodistribution of cysteine-containing Affibody molecules site-specifically labeled with (111)In, (99m)Tc, and (125)I at the C-terminus, having a His(6)-tag at the N- or C-terminus or a HEHEHE-tag at the N-terminus. We show that the use of a HEHEHE-tag provides appreciable reduction of hepatic radioactivity, especially for radiometal labels. We hope that this information can also be useful for development of other scaffold protein-based imaging agents.
authors.affiliation: Department of Molecular Biotechnology, Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Hofstrom
authors.forename: Anna
authors.initials: A
authors.lastname: Orlova
authors.forename: Mohamed
authors.initials: M
authors.lastname: Altai
authors.forename: Fredrik
authors.initials: F
authors.lastname: Wangsell
authors.forename: Torbjorn
authors.initials: T
authors.lastname: Graslund
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tolmachev
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D005260:Female; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D007205:Indium Radioisotopes; D007504:Iron Radioisotopes; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D009842:Oligopeptides / Q000737:chemistry; D015609:Organotechnetium Compounds; D011868:Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification* / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D003545:Cysteine; D018698:Glutamic Acid; D006639:Histidine; D007205:Indium Radioisotopes; D007504:Iron Radioisotopes; D009842:Oligopeptides; D015609:Organotechnetium Compounds; D011868:Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C471213:His-His-His-His-His-His; C515865:Z(HER2.4)2 affibody