Dataset Information

Unmasking the True Identity of Rapamycin's Minor Conformer.

ABSTRACT: Rapamycin, a well-known macrocyclic natural product with myriad biological activities, has been the subject of intense study since its first isolation and characterization over five decades ago. Rapamycin has been found to adopt a single conformation in the solid state (both when protein bound and uncomplexed) and exists as a mixture of two conformations in solution. Early work established that the major conformer in solution is the trans amide isomer but left the minor conformer mostly uncharacterized. Since that time, it has been widely accepted that the minor conformer of rapamycin is the cis amide, based solely on analogy to FK-506, another potent immunosuppressive compound with some shared key structural elements. To address this long-standing and unresolved question, the solution structure of the minor conformer of rapamycin was investigated using a combination of NMR techniques and computational methods and determined to be a trans amide species with rotation about the ester linkage.

SUBMITTER: Crull EB

PROVIDER: S-EPMC10391620 | biostudies-literature | 2023 Jul

REPOSITORIES: biostudies-literature

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Unmasking the True Identity of Rapamycin's Minor Conformer.

Crull Emily B EB Jain Ajay N AN Hawkins Paul C D PCD Cleves Ann E AE Graziani Edmund I EI Williamson R Thomas RT

Journal of natural products 20230711 7

Rapamycin, a well-known macrocyclic natural product with myriad biological activities, has been the subject of intense study since its first isolation and characterization over five decades ago. Rapamycin has been found to adopt a single conformation in the solid state (both when protein bound and uncomplexed) and exists as a mixture of two conformations in solution. Early work established that the major conformer in solution is the trans amide isomer but left the minor conformer mostly uncharac ...[more]

PMID: 37432113

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Project description:UnlabelledBackgroundPubChem is a free and publicly available resource containing substance descriptions and their associated biological activity information. PubChem3D is an extension to PubChem containing computationally-derived three-dimensional (3-D) structures of small molecules. All the tools and services that are a part of PubChem3D rely upon the quality of the 3-D conformer models. Construction of the conformer models currently available in PubChem3D involves a clustering stage to sample the conformational space spanned by the molecule. While this stage allows one to downsize the conformer models to more manageable size, it may result in a loss of the ability to reproduce experimentally determined "bioactive" conformations, for example, found for PDB ligands. This study examines the extent of this accuracy loss and considers its effect on the 3-D similarity analysis of molecules.ResultsThe conformer models consisting of up to 100,000 conformers per compound were generated for 47,123 small molecules whose structures were experimentally determined, and the conformers in each conformer model were clustered to reduce the size of the conformer model to a maximum of 500 conformers per molecule. The accuracy of the conformer models before and after clustering was evaluated using five different measures: root-mean-square distance (RMSD), shape-optimized shape-Tanimoto (STST-opt) and combo-Tanimoto (ComboTST-opt), and color-optimized color-Tanimoto (CTCT-opt) and combo-Tanimoto (ComboTCT-opt). On average, the effect of clustering decreased the conformer model accuracy, increasing the conformer ensemble's RMSD to the bioactive conformer (by 0.18 ± 0.12 Å), and decreasing the STST-opt, ComboTST-opt, CTCT-opt, and ComboTCT-opt scores (by 0.04 ± 0.03, 0.16 ± 0.09, 0.09 ± 0.05, and 0.15 ± 0.09, respectively).ConclusionThis study shows the RMSD accuracy performance of the PubChem3D conformer models is operating as designed. In addition, the effect of PubChem3D sampling on 3-D similarity measures shows that there is a linear degradation of average accuracy with respect to molecular size and flexibility. Generally speaking, one can likely expect the worst-case minimum accuracy of 90% or more of the PubChem3D ensembles to be 0.75, 1.09, 0.43, and 1.13, in terms of STST-opt, ComboTST-opt, CTCT-opt, and ComboTCT-opt, respectively. This expected accuracy improves linearly as the molecule becomes smaller or less flexible.

Dataset Information

Unmasking the True Identity of Rapamycin's Minor Conformer.

Publications

Unmasking the True Identity of Rapamycin's Minor Conformer.

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