Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms

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 hypoth...

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Cyhoeddwyd: Public Library of Science 2012
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Research Article
Mynediad Ar-lein:https://ncbi.nlm.nih.gov/pmc/articles/PMC3517587/
https://ncbi.nlm.nih.gov/pubmed/23236438
https://ncbi.nlm.nih.govhttp://dx.doi.org/10.1371/journal.pone.0051096
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id pubmed-3517587
record_format dspace
institution US National Library of Medicine
collection PubMed Central
language en
format Article
topic Research Article
spellingShingle Research Article
Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
topic_facet Research Article
description 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 isoform-specific 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.
author_sort Thomas, Elaine C.
title Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
title_short Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
title_full Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
title_fullStr Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
title_full_unstemmed Different Characteristics and Nucleotide Binding Properties of Inosine Monophosphate Dehydrogenase (IMPDH) Isoforms
title_sort different characteristics and nucleotide binding properties of inosine monophosphate dehydrogenase (impdh) isoforms
publisher Public Library of Science
publisher_facet Public Library of Science
publishDate 2012
url https://ncbi.nlm.nih.gov/pmc/articles/PMC3517587/
https://ncbi.nlm.nih.gov/pubmed/23236438
https://ncbi.nlm.nih.govhttp://dx.doi.org/10.1371/journal.pone.0051096
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