title: Chicken avidin-related proteins show altered biotin-binding and physico-chemical properties as compared with avidin.
abstract: Chicken avidin and bacterial streptavidin are proteins familiar from their use in various (strept)avidin-biotin technological applications. Avidin binds the vitamin biotin with the highest affinity known for non-covalent interactions found in nature. The gene encoding avidin (AVD) has homologues in chicken, named avidin-related genes (AVRs). In the present study we used the AVR genes to produce recombinant AVR proteins (AVRs 1, 2, 3, 4/5, 6 and 7) in insect cell cultures and characterized their biotin-binding affinity and biochemical properties. Amino acid sequence analysis and molecular modelling were also used to predict and explain the properties of the AVRs. We found that the AVR proteins are very similar to avidin, both structurally and functionally. Despite the numerous amino acid substitutions in the subunit interface regions, the AVRs form extremely stable tetramers similar to those of avidin. Differences were found in some physico-chemical properties of the AVRs as compared with avidin, including lowered pI, increased glycosylation and, most notably, reversible biotin binding for two AVRs (AVR1 and AVR2). Molecular modelling showed how the replacement Lys(111)-->isoleucine in AVR2 alters the shape of the biotin-binding pocket and thus results in reversible binding. Both modelling and biochemical analyses showed that disulphide bonds can form and link monomers in AVR4/5, a property not found in avidin. These, together with the other properties of the AVRs described in the present paper, may offer advantages over avidin and streptavidin, making the AVRs applicable for improved avidin-biotin technological applications.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FIN-40351 Jyväskylä, Finland.
authors.forename: Olli H
authors.initials: OH
authors.lastname: Laitinen
authors.forename: Vesa P
authors.initials: VP
authors.lastname: Hytönen
authors.forename: Mervi K
authors.initials: MK
authors.lastname: Ahlroth
authors.forename: Olli T
authors.initials: OT
authors.lastname: Pentikäinen
authors.forename: Ciara
authors.initials: C
authors.lastname: Gallagher
authors.forename: Henri R
authors.initials: HR
authors.lastname: Nordlund
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ovod
authors.forename: Ari T
authors.initials: AT
authors.lastname: Marttila
authors.forename: Eevaleena
authors.initials: E
authors.lastname: Porkka
authors.forename: Sanna
authors.initials: S
authors.lastname: Heino
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.forename: Kari J
authors.initials: KJ
authors.lastname: Airenne
authors.forename: Markku S
authors.initials: MS
authors.lastname: Kulomaa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001360:Avidin / Q000235:genetics / Q000378:metabolism*; D016367:Baculoviridae; D001710:Biotin / Q000378:metabolism*; D002645:Chickens; D006031:Glycosylation; D007525:Isoelectric Focusing; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D018411:Spodoptera; D019809:Streptavidin / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001360:Avidin; D001710:Biotin; D019809:Streptavidin