title: The periplasmic nitrate reductase from Escherichia coli: a heterodimeric molybdoprotein with a double-arginine signal sequence and an unusual leader peptide cleavage site.
abstract: The periplasmic nitrate reductase, NapA, from Escherichia coli was identified as a 90 kDa molybdoprotein which comigrated during polyacrylamide gel electrophoresis with the di-haem c-type cytochrome, NapB. The DNA sequence of the 5' end of the napA gene and the N-terminal amino acid sequences of both NapA and NapB were determined. The 36 residue leader peptide for NapA includes the double-arginine motif typical of proteins to which complex redox cofactors are attached in the cytoplasm prior to targeting to the periplasm. The pre-NapA leader sequence is both unexpectedly long and, unless two successive proteolysis steps are involved, is cleaved at the unprecedented sequence G-Q-Q-. Nap activity was suppressed during growth in the presence of tungstate and was absent from a mutant unable to synthesise the molybdopterin cofactor.
authors.affiliation: School of Biochemistry, University of Birmingham, UK.
authors.forename: G
authors.initials: G
authors.lastname: Thomas
authors.forename: L
authors.initials: L
authors.lastname: Potter
authors.forename: J A
authors.initials: JA
authors.lastname: Cole
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine; D001483:Base Sequence; D003067:Coenzymes; D003574:Cytochrome c Group / Q000302:isolation & purification*; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D008667:Metalloproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D009565:Nitrate Reductases / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D019897:Periplasm / Q000201:enzymology* / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics; D021382:Protein Sorting Signals / Q000235:genetics; D011621:Pteridines / Q000378:metabolism; D017973:Tungsten Compounds / Q000494:pharmacology
chemical_list: D001120:Arginine; D003067:Coenzymes; D003574:Cytochrome c Group; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D009565:Nitrate Reductases; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011621:Pteridines; D017973:Tungsten Compounds; C031732:cytochrome C-550; C022261:molybdopterin; C045951:tungstate