Different characteristics and nucleotide binding properties of Inosine Monophosphate Dehydrogenase (IMPDH) isoforms

Thomas, Elaine C., Gunter, Jennifer H., Webster, Julie A., Schieber, Nicole L., Oorschot, Viola, Parton, Robert G. and Whitehead, Jonathan P. (2012) Different characteristics and nucleotide binding properties of Inosine Monophosphate Dehydrogenase (IMPDH) isoforms. PloS One, 7 12: e51096.1-e51096.14. doi:10.1371/journal.pone.0051096

Author Thomas, Elaine C.
Gunter, Jennifer H.
Webster, Julie A.
Schieber, Nicole L.
Oorschot, Viola
Parton, Robert G.
Whitehead, Jonathan P.
Title Different characteristics and nucleotide binding properties of Inosine Monophosphate Dehydrogenase (IMPDH) isoforms
Journal name PloS One   Check publisher's open access policy
ISSN 1932-6203
Publication date 2012-12
Sub-type Article (original research)
DOI 10.1371/journal.pone.0051096
Open Access Status DOI
Volume 7
Issue 12
Start page e51096.1
End page e51096.14
Total pages 14
Place of publication San Francisco, CA, United States
Publisher Public Library of Science
Collection year 2013
Language eng
Formatted abstract
We recently reported that Inosine Monophosphate Dehydrogenase (IMPDH), a rate-limiting enzyme in de novo guanine nucleotide biosynthesis, clustered into macrostructures in response to decreased nucleotide levels and that there were
differences between the IMPDH isoforms, IMPDH1 and IMPDH2. We hypothesised that the Bateman domains, which are present in both isoforms and serve as energy-sensing/allosteric modules in unrelated proteins, would contribute to isoformspecific
differences and that mutations situated in and around this domain in IMPDH1 which give rise to retinitis pigmentosa (RP) would compromise regulation. We employed immuno-electron microscopy to investigate the ultrastructure of IMPDH macrostructures and live-cell imaging to follow clustering of an IMPDH2-GFP chimera in real-time. Using a series of IMPDH1/ IMPDH2 chimera we demonstrated that the propensity to cluster was conferred by the N-terminal 244 amino acids, which
includes the Bateman domain. A protease protection assay suggested isoform-specific purine nucleotide binding characteristics, with ATP protecting IMPDH1 and AMP protecting IMPDH2, via a mechanism involving conformational changes upon nucleotide binding to the Bateman domain without affecting IMPDH catalytic activity. ATP binding to  IMPDH1 was confirmed in a nucleotide binding assay. The RP-causing mutation, R224P, abolished ATP binding and nucleotide protection and this correlated with an altered propensity to cluster. Collectively these data demonstrate that (i) the isoforms are differentially regulated by AMP and ATP by a mechanism involving the Bateman domain, (ii) communication occurs between the Bateman and catalytic domains and (iii) the RP-causing mutations compromise such
regulation. These findings support the idea that the IMPDH isoforms are subject to distinct regulation and that regulatory defects contribute to human disease.
Keyword Dominant retinitis pigmentosa
Cystathionine beta synthase
Regulated protein kinase
Nucleic acid binding
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
Institute for Molecular Bioscience - Publications
UQ Diamantina Institute Publications
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Citation counts: TR Web of Science Citation Count  Cited 17 times in Thomson Reuters Web of Science Article | Citations
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