Fernández Claudio O, Niizeki Tomotake, Kohzuma Takamitsu, Vila Alejandro J
LANAIS RMN-300, University of Buenos Aires-CONICET, Junín 956, C1113AAD Buenos Aires, Argentina,
J Biol Inorg Chem. 2003 Jan;8(1-2):75-82. doi: 10.1007/s00775-002-0390-y. Epub 2002 Aug 29.
Pseudoazurin is an electron transfer copper protein, a member of the cupredoxin family. The protein is frequently found in denitrifying bacteria, where it is the electron donor of nitrite reductase. The copper at the active site is coordinated to His40, Cys78, His81 and Met86 in a distorted tetragonal geometry. We have recorded and assigned the (1)H NMR spectra of Co(II)-substituted pseudoazurin from Achromobacter cycloclastes. The (1)H NMR spectrum of Co(II)-pseudoazurin closely resembles that of Co(II)-rusticyanin, reflecting an altered conformation for the Met-Co(II)-Cys moiety in both proteins, compared to Co(II)-azurin, amicyanin and stellacyanin. The electron spin density onto the Sgamma(Cys) is larger in Co(II)-pseudoazurin compared to Co(II)-rusticyanin. Instead, the Co(II)-Met interaction is similar in both derivatives. Hence, the different metal-ligand interactions might be independently modulated by the protein structure. The present work also shows that the electron spin density onto the Co(II)-S(cys) bond is sensibly smaller than the Cu(II)-S(cys). Notwithstanding, NMR data on Co(II)-substituted blue copper proteins can be safely extrapolated to native Cu(II) proteins.
假蓝铜蛋白是一种电子传递铜蛋白，属于铜蓝蛋白家族。该蛋白常见于反硝化细菌中，是亚硝酸还原酶的电子供体。活性位点的铜以扭曲的四方几何结构与His40、Cys78、His81和Met86配位。我们记录并归属了来自环裂无色杆菌的Co(II)取代假蓝铜蛋白的(1)H NMR谱。Co(II) - 假蓝铜蛋白的(1)H NMR谱与Co(II) - 铁锈蛋白的谱非常相似，这反映出与Co(II) - 蓝铜蛋白、青紫蛋白和星蓝蛋白相比，这两种蛋白中Met - Co(II) - Cys部分的构象发生了改变。与Co(II) - 铁锈蛋白相比，Co(II) - 假蓝铜蛋白中Sγ(Cys)上的电子自旋密度更大。相反，两种衍生物中Co(II) - Met相互作用相似。因此，不同的金属 - 配体相互作用可能受蛋白质结构独立调节。目前的工作还表明，Co(II) - S(cys)键上的电子自旋密度明显小于Cu(II) - S(cys)。尽管如此，Co(II)取代的蓝色铜蛋白的NMR数据可以安全地外推到天然Cu(II)蛋白。
