Camelid nanobodies raised against an integral membrane enzyme, nitric oxide reductase,
Conrath, Katja, Pereira Alice S., Martins Carlos E., Timoteo Cristina G., Tavares Pedro, Spinelli Silvia, Kinne Joerg, Flaudrops Christophe, Cambillau Christian, Muyldermans Serge, Moura Isabel, Moura Jose J. G., Tegoni Mariella, and Desmyter Aline
, PROTEIN SCIENCE, Apr, Volume {18}, Number {3}, p.{619-628}, (2009)
AbstractNitric Oxide Reductase (NOR) is an integral membrane protein performing the reduction of NO to N(2)O. NOR is composed of two subunits: the large one (NorB) is a bundle of 12 transmembrane helices (TMH). It contains a b type heme and a binuclear iron site, which is believed to be the catalytic site, comprising a heme b and a non-hemic iron. The small subunit (NorC) harbors a cytochrome c and is attached to the membrane through a unique TMH. With the aim to perform structural and functional studies of NOR, we have immunized dromedaries with NOR and produced several antibody fragments of the heavy chain (VHHs, also known as nanobodies (TM)). These fragments have been used to develop a faster NOR purification procedure, to proceed to crystallization assays and to analyze the electron transfer of electron donors. BIAcore experiments have revealed that up to three VHHs can bind concomitantly to NOR with affinities in the nanomolar range. This is the first example of the use of VHHs with an integral membrane protein. Our results indicate that VHHs are able to recognize with high affinity distinct epitopes on this class of proteins, and can be used as versatile and valuable tool for purification, functional study and crystallization of integral membrane proteins.
CRYSTAL-STRUCTURE OF DESULFOREDOXIN FROM DESULFOVIBRIO-GIGAS DETERMINED AT 1.8 ANGSTROM RESOLUTION - A NOVEL NONHEME IRON PROTEIN-STRUCTURE,
Archer, M., Huber R., Tavares P., Moura I., Moura J. J. G., Carrondo M. A., Sieker L. C., Legall J., and Romão M. J.
, JOURNAL OF MOLECULAR BIOLOGY, Volume {251}, Number {5}, p.{690-702}, (1995)
AbstractThe crystal structure of desulforedoxin from Desulfovibrio gigas, a new homo-dimeric (2x36 amino acids) non-heme iron protein, has been solved by the SIRAS method using the indium-substituted protein as the single derivative. The structure was refined to a crystallographic X-factor of 16.9% at 1.8 Angstrom resolution. Native desulforedoxin crystals were grown from either PEG 4K or lithium sulfate, with cell constants a = b = 42.18 Angstrom, = 72.22 Angstrom (for crystals grown from PEG 4K), and they belong to space group P3(2)21. The indium-substituted protein crystallized isomorphously under the same conditions. The 2-fold symmetric dimer is firmly hydrogen bonded and folds as an incomplete beta-barrel with the two iron centers placed on opposite poles of the molecule. Each iron atom is coordinated to four cysteinyl residues in a distorted tetrahedral arrangement. Both iron atoms are 16 Angstrom apart but connected across the 2-fold axis by 14 covalent bonds along the polypeptide chain plus two hydrogen bonds. Desulforedoxin and rubredoxin share some structural features but show significant differences in terms of metal environment and water structure, which account for the known spectroscopic differences between rubredoxin and desulforedoxin. (C) 1995 Academic Press Limited