[Manganese-dependent ribonucleotide reductase of Propionibacterium freudenreichii subsp. shermanii: partial purification, characterization, and role in DNA biosynthesis].
Like Lactobacillus leichmanii, Rhizobium meliloti, and Euglena gracilis, P. freudenreichii implicates cobalamin in DNA anabolism via adenosylcobalamin-dependent ribonucleotide reductase. However, in the absence of corrinoids, P. freudenreichii is able to synthesize DNA with the involvement of an alternative ribonucleotide reductase, which is independent of adenosylcobalamin. This enzyme is localized in both the cytoplasm (80% of activity) and the cytoplasmic membrane (20% of activity), being loosely bound to the latter. Experiments with crude ribonucleotide reductase isolated from extracts of corrinoid-deficient cells showed that manganese specifically stimulates this enzyme and that it is composed of two protein subunits, a feature that is typical of all metal-containing reductases activated by molecular oxygen. Low concentrations of manganese ions enhanced DNA synthesis in corrinoid-deficient manganese-limited cells. This effect was prevented by the addition of 80 mM hydroxyurea, a specific inhibitor of metal-containing aerobic ribonucleotide reductases. It was concluded that, in adenosylcobalamin-deficient P. freudenreichii cells, DNA synthesis is provided with deoxyribosyl precursors through the functioning of manganese-dependent aerobic ribonucleotide reductase composed of two subunits.
Iordan
E P
EP
Department of Microbiology, Faculty of Biology, Moscow State University, Vorob'evy gory, Russia.
Bryukhanov
A L
AL
Dunaevskiĭ
Ia E
IaE
Pryanishnikova
N I
NI
Danilova
I V
IV
D002462:Cell Membrane / Q000201:enzymology; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003593:Cytoplasm / Q000201:enzymology; D004269:DNA, Bacterial / Q000096:biosynthesis*; D008345:Manganese / Q000378:metabolism*; D011424:Propionibacterium / Q000201:enzymology*; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D004269:DNA, Bacterial; D008345:Manganese; D012264:Ribonucleotide Reductases