PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 16138306

Pseudoazurin-nitrite reductase interactions.

Antonietta Impagliazzo·Ludwig Krippahl·Marcellus Ubbink
View original source ↗Export metadata ↓

Abstract

The nitrite reductase-binding site on pseudoazurin has been determined by using NMR chemical-shift perturbations. It comprises residues in the hydrophobic patch surrounding the exposed copper ligand His81 as well as several positively charged residues. The binding site is similar for both redox states of pseudoazurin, despite differences in the binding mode. The results suggest that pseudoazurin binds in a well-defined orientation. Docking simulations provide a putative structure of the complex with a binding site on nitrite reductase that has several hydrophobic and polar residues as well as a ridge of negatively charged side chains and a copper-to-copper distance of 14 A.

Explore related subjects

AzurinCopperModels, MolecularNitrite ReductasesNuclear Magnetic Resonance, BiomolecularProtein BindingProtein Structure, QuaternaryJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Antonietta Impagliazzo, Ludwig Krippahl, Marcellus Ubbink. 2005. Pseudoazurin-nitrite reductase interactions.. https://doi.org/10.1002/cbic.200500082

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Engineering copper sites in proteins: loops confer native structures and properties to chimeric cupredoxins.

The ligand-containing loops of two copper-binding electron-transfer proteins (cupredoxins) have been swapped. In the azurin (AZ) variant in which the plastocyanin (PC) sequence is introduced (AZPC), the loop adopts a conformation identical to that in PC. The reduction potential of AZPC is raised as compared to AZ and matches that of PC. In the previously published AZAMI variant (AMI = amicyanin), the shorter introduced loop adopts the same conformation as in AMI, and the reduction potential is lowered to equal that of AMI (Yanagisawa, S.; Dennison, C. J. Am. Chem. Soc. 2004, 126, 15711-15719. Li, C.; et al. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 7258-7263). Thus, the loop structure plays an important role in tuning the reduction potential of a type 1 copper site with contributions from protein dipoles in this region probably the most important feature. The structure of the loop also seems to be a major factor in controlling dissociation and protonation of the C-terminal His ligand, which can act as a switch to regulate electron-transfer reactivity. The PCAZ variant (PC with the AZ loop) possesses an active site, which is different from those of both PC and AZ, and it is assumed that the introduced loop does not adopt a structure as in AZ. This contributes to the observed instability of PCAZ and highlights that loop-scaffold interactions are important for stabilizing the active site of a cupredoxin.

Azurin↗
PubMed2007

Conserved water molecular dynamics of the different X-ray structures of rusticyanin: an unique aquation potentiality of the ligand bonded Cu++ center.

The invariant water molecular interaction involving in the Rusticyanin of Thiobacillus ferrooxidans is thought to be important for its molecular complexation with other proteins at differential acidophilic situation. The comparative analysis of the different x-ray, energy minimized, and auto solvated structures of Rusticyanin revealed the presence of five specific invariant bound water molecules (among the approximately 150 water molecules per monomer) in the crystals. The five W 205, W 206, W 112, W 214, and W 221 water molecules (in Rusticyanin PDB code: 1RCY) were seem to be invariant in all the seven structures (PDB codes: 1RCY, 1A3Z, 1A8Z, 1E3O, 1GY1, 1GY2, 2CAL). Among the five conserved water molecules the W 221 (of 1 RCY or the equivalent water molecules in the other oxidized form of Rusticyanin structures) had endowed an interesting coordination potentiality to Cu(+2) ion during the energy minimization. The W 221 was observed to approach toward the tetrahedrally bonded Cu(+2) ion through the opposite (or trans) route of metal-bonded Met 148. This direct water molecular coordination affected the tetrahedral geometry of Cu(+2) to trigonal bipyramidal. Presumably this structural dynamics at the Cu(+2) center could involve in the electron transport process during protein-protein complexation.

Azurin↗
PubMed2006

Protein stability in ice.

This study presents an experimental approach, based on the change of Trp fluorescence between native and denatured states of proteins, which permits to monitor unfolding equilibria and the thermodynamic stability (DeltaG degrees ) of these macromolecules in frozen aqueous solutions. The results obtained by guanidinium chloride denaturation of the azurin mutant C112S from Pseudomonas aeruginosa, in the temperature range from -8 to -16 degrees C, demonstrate that the stability of the native fold may be significantly perturbed in ice depending mainly on the size of the liquid water pool (V(L)) in equilibrium with the solid phase. The data establish a threshold, around V(L)=1.5%, below which in ice DeltaG degrees decreases progressively relative to liquid state, up to 3 kcal/mole for V(L)=0.285%. The sharp dependence of DeltaG degrees on V(L) is consistent with a mechanism based on adsorption of the protein to the ice surface. The reduction in DeltaG degrees is accompanied by a corresponding decrease in m-value indicating that protein-ice interactions increase the solvent accessible surface area of the native fold or reduce that of the denatured state, or both. The method opens the possibility for examining in a more quantitative fashion the influence of various experimental conditions on the ice perturbation and in particular to test the effectiveness of numerous additives used in formulations to preserve labile pharmaco proteins.

Azurin↗