NMR Solution Structure of Cu(I) Rusticyanin fromThiobacillus ferrooxidans: Structural Basis for the Extreme Acid Stability and Redox Potential

Interaction-induced Redox Switch in the Electron Transfer Complex Rusticyanin-Cytochrome c 4

“…a blueshift of the charge transfer band from 597 to 577 nm (11). Apart from the blueshift, the charge transfer band was seen to persist up to pH values of about 10, demonstrating that the overall distorted tetrahedral ligand geometry (involving one cysteine-, one methionine, and two histidine residues (24,25), see Fig. 6) was maintained up to this pH value.…”

“…Rusticyanin, by contrast, is an acid-stable protein and the pK value of the N ␦ protonation site therefore needs to be shifted to pH values significantly below pH 2 in order to assure integrity of the copper site at the physiological pH values of the organism (24,25). Consequently, the above described pK value on the reduced form of the protein was not observed in RCy (26).…”

The Multicenter Aerobic Iron Respiratory Chain of Acidithiobacillus ferrooxidans Functions as an Ensemble with a Single Macroscopic Rate Constant

“…The latter value compares favorably with those of 330 mg/ml for hemoglobin in red blood cells (42) and 300 -400 mg/ml for macromolecules in the interior of Escherichia coli (43). The volume of a single rusticyanin molecule is ϳ20 nm 3 , as determined using either the value of 0.73 cm 3 /g for the average partial specific volume of a globular protein (44) or the actual dimensions of the purified rusticyanin obtained from structural studies by x-ray crystallographic (45) or multidimensional NMR means (46). Consequently, the rusticyanin protein at 350 mg/ml occupies 4.6 ϫ 10 16 nm 3 or 21% of the total volume in the periplasmic space.…”

Respiratory Isozyme, Two Types of Rusticyanin ofAcidithiobacillus ferrooxidans

“…Figure 6 shows that when the diŠerence in the amino acids sequences of the 23270-A and 3865-B proteins were imposed on a model of the tertiary structure of rusticyanin, 20,43) four (33Gly-Ala, 34Thr-Pro, 38Thr-Ser, and 41Glu-Met) of the eighteen residues were not involved in the model because they are within a ‰exible amino-terminal helix facing the solution. Nine (52Glu-Ala, 55Thr-Ser, 61Asp-Lys, 91Lys-Val, 97Glu-Asp, 149Asp-Ser, 151Lys-Gly, 160His-Arg, and 162Thr-Ala) of the remaining fourteen residues were located on the surface of the molecule, resulting in a net loss of 5 negative charges in type-B rusticyanin at neutral pH-i.e., the type-B protein was less acidic than the type-A protein, which likely accounts for the change in the mobility seen on native-PAGE (Fig.…”

“…It is known that the hydrophobic and electrolytic interactions in the patch surrounding the copper coordination sphere contribute to the acidstability and redox potential of this protein. 19,20,43) Theseˆve replacements may in‰uence the copper coordination center and thus account for the decrease of the molecular coe‹cient and ESR signal of the type-B protein (Fig. 4).…”