title: Electron transport-linked proton translocation at nitrite reduction in Campylobacter sputorum subspecies bubulus.
abstract: Campylobacter sputorum subspecies bubulus contains a membrane-bound nitrite reductase which catalyses the six-electron reduction of nitrite to ammonia. Formate and L-lactate are used as hydrogen donors. Cells of C. sputorum grown with nitrate or nitrite contain cytochromes of the b- and c-type and a carbon monoxide-binding cytochrome c. In addition, a special membrane-bound carbon monoxide-binding pigment is found. Nitrite reduction with formate or L-lactate as a hydrogen donor is strongly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Nitrite reduction by bacterial suspensions with lactate as a hydrogen donor is strongly inhibited by carbonylcyanide-m-chlorophenylhydrazone (CCCP) whereas nitrite reduction with formate as a hydrogen donor is not inhibited at all. Leads to H+/O values and leads to H+/NO-2 values were measured with ascorbate + N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formate (in the absence and presence of carbonic anhydrase) and L-lactate as a hydrogen donor. The results are summarized in a scheme for electron transport from formate or lactate to oxygen or nitrite which shows a periplasmic orientation of formate dehydrogenase and nitrite reductase and a cytoplasmic orientation of lactate dehydrogenase and oxygen reduction, and which shows proton translocation with a leads to H+/2e value of 2.0. The leads to H+/O and leads to H+/NO-2 values predicted by this scheme are in good agreement with the experimental values.
mesh_terms: D002167:Campylobacter / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003573:Cytochrome b Group; D003574:Cytochrome c Group / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism; D004579:Electron Transport; D005561:Formates / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D009572:Nitrite Reductases / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D003580:Cytochromes; D005561:Formates; D007773:Lactates; D009573:Nitrites; D019344:Lactic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006859:Hydrogen; D009572:Nitrite Reductases