Assignment of haem ligands and detection of electronic absorption bands of molybdenum in the di‐haem periplasmic nitrate reductase of Paracoccus pantotrophus

FEBS Letters

Butler, Clive S.²  Cheesman, Myles R.²  Ferguson, Stuart J.¹  Berks, Ben C.²  Richardson, David J.²  Thomson, Andrew J.² 

[1] Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK;Centre for Metalloprotein Spectroscopy and Biology, School of Biological and Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK

关键词: Magnetic circular dichroism spectroscopy;    Electron paramagnetic resonance spectroscopy;    Heme ligand;    Molybdoenzyme;    MGD;    molybdopterin guanine dinucleotide;    NAP;    periplasmic nitrate reductase;    DMSOR;    dimethyl sulfoxide reductase;    EPR;    electron paramagnetic resonance;    MCD;    magnetic circular dichroism;   

DOI  :  10.1016/S0014-5793(01)02577-7

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The periplasmic nitrate reductase (NAP) from Paracoccus pantotrophus is a soluble two-subunit enzyme (NapAB) that binds two c-type haems, a [4Fe–4S] cluster and a bis-molybdopterin guanine dinucleotide cofactor that catalyses the reduction of nitrate to nitrite. In the present work the NapAB complex has been studied by magneto-optical spectroscopy to probe co-ordination of both the NapB haems and the NapA active site Mo. The absorption spectrum of the NapAB complex is dominated by features from the NapB c-type cytochromes. Using a combination of electron paramagnetic resonance spectroscopy and magnetic circular dichroism it was demonstrated that both haems are low-spin with bis-histidine axial ligation. In addition, a window between 600 and 800 nm was identified in which weak absorption features that may arise from Mo could be detected. The low-temperature MCD spectrum shows oppositely signed bands in this region (peak 648 nm, trough 714 nm) which have been assigned to S-to-Mo(V) charge transfer transitions.

【 授权许可】

Unknown