Inosine 5'-monophosphate dehydrogenase binds nucleic acids in vitro and in vivo.
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.
McLean
Jeremy E
JE
Program in Biophysics and Structural Biology, Brandeis University, MS 009, 415 South St., Waltham, MA 02454, USA.
Hamaguchi
Nobuko
N
Belenky
Peter
P
Mortimer
Sarah E
SE
Stanton
Martin
M
Hedstrom
Lizbeth
L
D001665:Binding Sites; D002467:Cell Nucleus / Q000201:enzymology; D004247:DNA / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D006801:Humans; D007168:IMP Dehydrogenase / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D009696:Nucleic Acids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism*; D014466:Ultraviolet Rays
D004277:DNA, Single-Stranded; D009696:Nucleic Acids; D012313:RNA; D004247:DNA; D007168:IMP Dehydrogenase