title: Structure and characterization of a novel chicken biotin-binding protein A (BBP-A).
abstract: BACKGROUND
  The chicken genome contains a BBP-A gene showing similar characteristics to avidin family genes. In a previous study we reported that the BBP-A gene may encode a biotin-binding protein due to the high sequence similarity with chicken avidin, especially at regions encoding residues known to be located at the ligand-binding site of avidin.
  
  
  RESULTS
  Here, we expand the repertoire of known macromolecular biotin binders by reporting a novel biotin-binding protein A (BBP-A) from chicken. The BBP-A recombinant protein was expressed using two different expression systems and purified with affinity chromatography, biochemically characterized and two X-ray structures were solved - in complex with D-biotin (BTN) and in complex with D-biotin D-sulfoxide (BSO). The BBP-A protein binds free biotin with high, "streptavidin-like" affinity (Kd ~ 10-13 M), which is about 50 times lower than that of chicken avidin. Surprisingly, the affinity of BBP-A for BSO is even higher than the affinity for BTN. Furthermore, the solved structures of the BBP-A--BTN and BBP-A--BSO complexes, which share the fold with the members of the avidin and lipocalin protein families, are extremely similar to each other.
  
  
  CONCLUSIONS
  BBP-A is an avidin-like protein having a beta-barrel fold and high affinity towards BTN. However, BBP-A differs from the other known members of the avidin protein family in thermal stability and immunological properties. BBP-A also has a unique ligand-binding property, the ability to bind BTN and BSO at comparable affinities. BBP-A may have use as a novel material in, e.g. modern bio(nano)technological applications.
authors.affiliation: NanoScience Center, Department of Biological and Environmental Science, P.O. Box 35 (YAB), FI-40014 University of Jyväskylä, Finland. veshyto@mat.ethz.ch <veshyto@mat.ethz.ch>
authors.forename: Vesa P
authors.initials: VP
authors.lastname: Hytönen
authors.forename: Juha A E
authors.initials: JA
authors.lastname: Määttä
authors.forename: Einari A
authors.initials: EA
authors.lastname: Niskanen
authors.forename: Juhani
authors.initials: J
authors.lastname: Huuskonen
authors.forename: Kaisa J
authors.initials: KJ
authors.lastname: Helttunen
authors.forename: Katrin K
authors.initials: KK
authors.lastname: Halling
authors.forename: Henri R
authors.initials: HR
authors.lastname: Nordlund
authors.forename: Kari
authors.initials: K
authors.lastname: Rissanen
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.forename: Tiina A
authors.initials: TA
authors.lastname: Salminen
authors.forename: Markku S
authors.initials: MS
authors.lastname: Kulomaa
authors.forename: Olli H
authors.initials: OH
authors.lastname: Laitinen
authors.forename: Tomi T
authors.initials: TT
authors.lastname: Airenne
mesh_terms: D000818:Animals; D001360:Avidin / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002645:Chickens; D003460:Crystallization; D036103:Nanotechnology; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D002352:Carrier Proteins; C017071:biotin-binding proteins; D001360:Avidin