Inosine 5'-monophosphate dehydrogenase binds nucleic acids in vitro and in vivo.
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McLean JE, Hamaguchi N, Belenky P, Mortimer SE, Stanton M, Hedstrom L
Inosine 5'-monophosphate dehydrogenase binds nucleic acids in vitro and in vivo.
Biochem J. 2004 Apr 15;379(Pt 2):243-51.
- PubMed ID
- 14766016 [ View in PubMed]
- Abstract
Inosine 5'-monophosphate dehydrogenase (IMPDH) is the rate-limiting enzyme in the de novo biosynthesis of guanine nucleotides. In addition to the catalytic domain, IMPDH contains a subdomain of unknown function composed of two cystathione beta-synthase domains. Our results, using three different assays, show that IMPDHs from Tritrichomonas foetus, Escherichia coli, and both human isoforms bind single-stranded nucleic acids with nanomolar affinity via the subdomain. Approx. 100 nucleotides are bound per IMPDH tetramer. Deletion of the subdomain decreases affinity 10-fold and decreases site size to 60 nucleotides, whereas substitution of conserved Arg/Lys residues in the subdomain with Glu decreases affinity by 20-fold. IMPDH is found in the nucleus of human cells, as might be expected for a nucleic-acid-binding protein. Lastly, immunoprecipitation experiments show that IMPDH binds both RNA and DNA in vivo. These experiments indicate that IMPDH has a previously unappreciated role in replication, transcription or translation that is mediated by the subdomain.