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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Amino Acid Sequence
-
Arginine
-
Base Sequence
-
Coenzymes*
-
Cytochrome c Group / isolation & purification*
-
Dimerization
-
Escherichia coli / enzymology*
-
Escherichia coli / genetics
-
Metalloproteins / metabolism
-
Molecular Sequence Data
-
Molybdenum Cofactors
-
Molybdenum*
-
Nitrate Reductases / drug effects
-
Nitrate Reductases / genetics
-
Nitrate Reductases / isolation & purification*
-
Periplasm / enzymology*
-
Periplasm / genetics
-
Protein Precursors / genetics
-
Protein Sorting Signals / genetics
-
Pteridines / metabolism
-
Tungsten Compounds / pharmacology
Substances
-
Coenzymes
-
Cytochrome c Group
-
Metalloproteins
-
Molybdenum Cofactors
-
Protein Precursors
-
Protein Sorting Signals
-
Pteridines
-
Tungsten Compounds
-
Molybdenum
-
cytochrome C-550
-
Arginine
-
molybdenum cofactor
-
Nitrate Reductases
-
tungstate