Ribonucleotide reductase catalytic subunit M1 (RRM1) allosteric activity site (RRM1 A-site)

Human ribonucleotide reductase (RNR) is the rate-limiting enzyme responsible for the de novo production of deoxyribonucleotides (dNTPs), which are essential building blocks for DNA replication and repair [1][2]. The enzyme is a complex heterotetramer, and its activity is tightly controlled by the allosteric activity site (A-site) located on the large catalytic subunit, RRM1 [1][3]. This A-site acts as a master switch: the binding of ATP activates the enzyme to maintain dNTP production, while the binding of dATP induces a conformational change that promotes the formation of inactive α6β2 hexamers, effectively shutting down the enzyme [3][4]. This regulatory mechanism is a major target for several chemotherapeutic nucleoside analogs, such as clofarabine and fludarabine [5]. These drugs are intracellularly phosphorylated into triphosphate metabolites that bind to the A-site with high affinity, mimicking the inhibitory effect of dATP [4][6]. By locking the enzyme in an inactive state, these agents cause a profound depletion of dNTP pools, leading to replication fork collapse, DNA damage, and the induction of apoptosis in rapidly proliferating cancer cells [5][6]. Sources: [1] UniProt Consortium. UniProtKB - P23921 (RRM1_HUMAN). [2] Nordlund, P., & Reichard, P. (2006). Ribonucleotide Reductases. Annual Review of Biochemistry. [3] Fairman, J. W., et al. (2011). Structural basis for allosteric regulation of human ribonucleotide reductase by nucleotide-induced oligomerization. Nature Structural & Molecular Biology. [4] Greene, B. L., et al. (2015). Ribonucleotide Reductases: Structure, Mechanism, and Drug Discovery. Drug Discovery Today. [5] Parker, W. B. (2009). Enzymology of Purine and Pyrimidine Antimetabolites Used in the Treatment of Cancer. Chemical Reviews. [6] Bonate, P. L., et al. (2006). Discovery and development of clofarabine: a nucleoside analogue for treating cancer. Nature Reviews Drug Discovery.

Other names

Human ribonucleotide reductase allosteric A siteRNR activity siteRNR A-siteRibonucleoside-diphosphate reductase large subunit allosteric siteRRM1 allosteric activity site

Allosteric inhibition of enzyme activity via induction of inactive oligomerization (hexamerization) or competitive displacement of activating ATP.