Inhibition of Branched-Chain α-Keto Acid Dehydrogenase Kinase and Sln1 Yeast Histidine Kinase by the Antifungal Antibiotic Radicicol

Abstract

The 90-kDa heat shock family (HSP90) of protein and twocomponent histidine kinases, although quite distinct at the primary amino acid sequence level, share a common structural ATP-binding domain known as the Bergerat fold. The Bergerat fold is important for the ATPase activity and associated chaperone function of HSP90. Two-component histidine kinases occur in bacteria, yeast, and plants but have yet to be identified in mammalian cells. The antifungal antibiotic radicicol (Monorden) has been shown to bind to the Bergerat fold of HSP90 and to inhibit its ATPase activity. The structural similarity between the Bergerat fold of HSP90 and bacterial two-component histidine kinases prompted our inquiry into whether radicicol could be a potential inhibitor of histidine kinase-like proteins. Structural homology searches suggest that the ATP-binding domains of the yeast histidine kinase Sln1 and the mammalian, branched-chain ␣-keto acid dehydrogenase kinase are very similar to that of other Bergerat fold family members. On the basis of structural homology, we tested radicicol as a potential inhibitor of Sln1 and branched-chain ␣-keto acid dehydrogenase kinase (BCKDHK) and propose a mechanism of inhibition of these kinases. Although BCKDHK has been shown to have serine autophosphorylation activity, we speculate, based on the results from this study and other supporting evidence, that BCKDHK may also have intrinsic histidine kinase activity.

JX06 Selectively Inhibits Pyruvate Dehydrogenase Kinase PDK1 by a Covalent Cysteine Modification

“…A few PDK1 inhibitors have been reported, including the ATP competitive inhibitor radicicol, allosteric inhibitor dichloroacetate (DCA), and AZD7545 that disrupts PDK1 interaction with the PDC component (21)(22)(23)(24). Among these inhibitors, DCA is the only one showing preliminary clinical efficacy in a small cohort of patients with glioblastoma (25).…”

Bacterial protein kinase inhibitors

“…The ATP-binding domain of histidine kinases has similar topology to those of a family of eukaryotic ATPases including DNA gyrase, and the 90-kDa heat shock family (Hsp90); they share a common structural ATP-binding domain known as the Bergerat fold [Bilwes et al, 1999]. Indeed, the antifungal radicicol (monorden, 1), a known binder of the Bergerat fold of Hsp90 with its ATPase activity, was a competitive ATP inhibitor of the yeast histidine kinase, Sln1 [Besant et al, 2002] (see Fig. 2).…”

The histidine kinase inhibitor Sda binds near the site of autophosphorylation and may sterically hinder autophosphorylation and phosphotransfer to Spo0F

“…6A), Histidine kinases have long been considered attractive targets for the development of new antimicrobial drugs (Macielag and Goldschmidt, 2000;Matsushita and Janda, 2002;Hubbard et al, 2003;Lyon and Muir, 2003;Stephenson and Hoch, 2004;Rowland and King, 2007). Specific inhibitors of histidine kinases have recently been reported based on lead compounds that were identified by high-throughput screening of chemical libraries or from the rational design of compounds (Lyon et al, 2000;Besant et al, 2002;Foster et al, 2004;Gilmour et al, 2005;Qin et al, 2006;Okada et al, 2007). The surface that we have identified as being important for Sda and KipI to inhibit KinA may prove useful as a new target for the rational design of compounds that bind and inhibit histidine kinases.…”