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Nucleic Acids Res. 2011 Mar;39(4):1381-9. doi: 10.1093/nar/gkq924. Epub 2010 Oct 23.

Assembly of a fragmented ribonucleotide reductase by protein interaction domains derived from a mobile genetic element.

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  • 1Department of Molecular Biology and Functional Genomics, Stockholm University, S-10691 Stockholm, Sweden.

Abstract

Ribonucleotide reductase (RNR) is a critical enzyme of nucleotide metabolism, synthesizing precursors for DNA replication and repair. In prokaryotic genomes, RNR genes are commonly targeted by mobile genetic elements, including free standing and intron-encoded homing endonucleases and inteins. Here, we describe a unique molecular solution to assemble a functional product from the RNR large subunit gene, nrdA that has been fragmented into two smaller genes by the insertion of mobE, a mobile endonuclease. We show that unique sequences that originated during the mobE insertion and that are present as C- and N-terminal tails on the split NrdA-a and NrdA-b polypeptides, are absolutely essential for enzymatic activity. Our data are consistent with the tails functioning as protein interaction domains to assemble the tetrameric (NrdA-a/NrdA-b)(2) large subunit necessary for a functional RNR holoenzyme. The tails represent a solution distinct from RNA and protein splicing or programmed DNA rearrangements to restore function from a fragmented coding region and may represent a general mechanism to neutralize fragmentation of essential genes by mobile genetic elements.

PMID:
20972217
[PubMed - indexed for MEDLINE]
PMCID:
PMC3045599
Free PMC Article
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