THE NOS (NITROUS-OXIDE REDUCTASE) GENE-CLUSTER FROM THE SOIL BACTERIUM ACHROMOBACTER CYCLOCLASTES - CLONING, SEQUENCE-ANALYSIS, AND EXPRESSION

The nitrous oxide (N2O) reductase (nos) gene cluster from Achromobacte r cycloclastes has been cloned and sequenced. Seven protein coding reg ions corresponding to nosR, nosZ (structural N2O reductase gene), nosD , nosF, nosY, nosL, and nosX are detected, indicating a genetic organi zation similar to that of Rhizobium meliloti. To aid homology studies, nosR from R. meliloti has also been sequenced. Comparison of the dedu ced amino acid sequences with corresponding sequences from other organ isms has also allowed structural and functional inferences to be made. The heterologous expression of NosD, NosZ (N2O reductase), and NosL i s also reported. A model of the Cu-A Site in N2O reductase, based on t he crystal structure of this site in bovine heart cytochrome c oxidase , is presented. The model suggests that a His residue of the Cu-A doma in may be a ligand to the catalytic Cu-Z site. In addition, the origin of the spectroscopically-observed Cys coordination to Cu-Z is discuss ed in terms of the sequence alignment of seven N2O reductases. (C) 199 8 Elsevier Science Inc. All rights reserved.