A bacterial c-type cytochrome can be translocated to the periplasm as an apo form; the biosynthesis of cytochrome cd1 (nitrite reductase) from Paracoccus denitrificans.
An apo form of cytochrome cd1 (nitrite reductase) of Paracoccus denitrificans has been detected immunologically in the periplasm of a mutant that lacks all c-type cytochromes. A method for the preparation of apo-nitrite reductase (lacking both c- and d-type haem) from the holoenzyme of wild-type cells has been developed. The apoprotein synthesized by the mutant is indistinguishable from the chemically prepared apoprotein in respect of: (i) subunit molecular weight; (ii) formation of a homodimer; (iii) properties on anion exchange chromatography. The holoenzyme has similar properties in respect of (i) and (ii) but behaves differently during anion exchange. A suggested mode of assembly of cytochrome cd1 is translocation into the periplasm of a precursor polypeptide, maturation by a signal peptidase to give an apoprotein identical to that prepared chemically from the holoenzyme, followed by insertion of c-type and d-type haem in an as yet unknown order.
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MD
Department of Biochemistry, University of Oxford, UK.
Ferguson
S J
SJ
D001059:Apoproteins / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002851:Chromatography, High Pressure Liquid; D003574:Cytochrome c Group / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c; D004591:Electrophoresis, Polyacrylamide Gel; D007158:Immunologic Techniques; D008970:Molecular Weight; D009154:Mutation; D009572:Nitrite Reductases; D010231:Paracoccus denitrificans / Q000201:enzymology* / Q000254:growth & development; D021382:Protein Sorting Signals
D001059:Apoproteins; D003574:Cytochrome c Group; D003580:Cytochromes; D021382:Protein Sorting Signals; D045304:Cytochromes c; C019315:cytochrome cd1; D009572:Nitrite Reductases