The Manganese-containing Ribonucleotide Reductase of Corynebacterium ammoniagenes is a Class Ib Enzyme
Fieschi, Frank (Stockholms universitet. Institutionen för molekylärbiologi)
Torrents Serra, Eduard (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Toulokhonova, Larisa (Stockholms universitet. Institutionen för molekylärbiologi)
Jordan, Albert (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Hellman, Ulf (Ludwig Institute for Cancer Research)
Barbé García, Jordi (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Gibert, Isidre (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Karlsson, Margareta (Stockholms universitet. Institutionen för molekylärbiologi)
Sjöberg, Britt-Marie (Stockholms universitet. Institutionen för molekylärbiologi)

Data:	1998
Resum:	Ribonucleotide reductases (RNRs) are key enzymes in living cells that provide the precursors of DNA synthesis. The three characterized classes of RNRs differ by their metal cofactor and their stable organic radical. We have purified to near homogeneity the enzymatically active Mn-containing RNR of Corynebacterium ammoniagenes, previously claimed to represent a fourth RNR class. N-terminal and internal peptide sequence analyses clearly indicate that the C. ammoniagenes RNR is a class Ib enzyme. In parallel, we have cloned a 10-kilobase pair fragment from C. ammoniagenes genomic DNA, using primers specific for the known class Ib RNR. The cloned class Ib locus contains the nrdHIEF genes typical for class Ib RNR operon. The deduced amino acid sequences of the nrdE and nrdF genes matched the peptides from the active enzyme, demonstrating that C. ammoniagenes RNR is composed of R1E and R2F components typical of class Ib. We also show that the Mn-containing RNR has a specificity for the NrdH-redoxin and a response to allosteric effectors that are typical of class Ib RNRs. Electron paramagnetic resonance and atomic absorption analyses confirm the presence of Mn as a cofactor and show, for the first time, insignificant amounts of iron and cobalt found in the other classes of RNR. Our discovery that C. ammoniagenes RNR is a class Ib enzyme and possesses all the highly conserved amino acid side chains that are known to ligate two ferric ions in other class I RNRs evokes new, challenging questions about the control of the metal site specificity in RNR. The cloning of the entire NrdHIEF locus of C. ammoniagenes will facilitate further studies along these lines.
Ajuts:	Ministerio de Educación y Ciencia PB94-0687
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	DNA ; Ribonucleotide reductase ; RNR
Publicat a:	Journal of biological chemistry, Vol. 273, No. 8 (Feb. 1998) , p. 4329-4337, ISSN 1083-351X

DOI: 10.1074/jbc.273.8.4329

10 p, 205.3 KB

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