pH-profile crystal structure studies of C-terminal despentapeptide nitrite reductase from Achromobacter cycloclastes.
Crystal structures of C-terminal despentapeptide nitrite reductase (NiRc-5) from Achromobacter cycloclastes were determined from 1.9 to 2.3A at pH 5.0, 5.4, and 6.2. NiRc-5, that has lost about 30% activity, is found to possess quite similar trimeric structures as the native enzyme. Electron density and copper content measurements indicate that the activity loss is not caused by the release of type 2 copper (T2Cu). pH-profile structural comparisons with native enzyme reveal that the T2Cu active center in NiRc-5 is perturbed, accounting for the partial loss of enzyme activity. This perturbation likely results from the less constrained conformations of two catalytic residues, Asp98 and His255. Hydrogen bonding analysis shows that the deletion of five residues causes a loss of more than half the intersubunit hydrogen bonds mediated by C-terminal tail. This study shows that the C-terminal tail plays an important role in controlling the conformations around the T2Cu site at the subunit interface, and helps keep the optimum microenvironment of active center for the full enzyme activity of AcNiR.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15th Datun Road, Chaoyang District, Beijing 100101, China.
Hai-Tao
HT
Li
Chao
C
Wang
Tschining
T
Chang
Wen-Chang
WC
Chang
Ming-Yih
MY
Liu
Jean
J
Le Gall
Lu-Lu
LL
Gui
Ji-Ping
JP
Zhang
Xiao-Min
XM
An
Wen-Rui
WR
Chang
D042422:Achromobacter cycloclastes / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D003300:Copper / Q000032:analysis; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009572:Nitrite Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
D001426:Bacterial Proteins; D003300:Copper; D009572:Nitrite Reductases