Biomedical subjects

Per Källblad

Publications and source records attributed to Per Källblad.

7 recordsLinked to original sources

PubMed2005

Isoindolinone-based inhibitors of the MDM2-p53 protein-protein interaction.

A series of 2-N-alkyl-3-aryl-3-alkoxyisoindolinones has been synthesised and evaluated as inhibitors of the MDM2-p53 interaction. The most potent compound, 3-(4-chlorophenyl)-3-(4-hydroxy-3,5-dimethoxybenzyloxy)-2-propyl-2,3-dihydroisoindol-1-one (NU8231), exhibited an IC50 of 5.3 +/- 0.9 microM in an ELISA assay, and induced p53-dependent gene transcription in a dose-dependent manner, in the SJSA human sarcoma cell line.

Cell Line, Tumor↗

PubMed2004

Backbone-backbone geometry of tertiary contacts between alpha-helices.

Knowledge about how secondary-structure elements combine together to form the tertiary structure is crucial for understanding protein folding. We have examined packing solutions for alpha-helices by performing a crystal survey of the underlying backbone-backbone inter-geometry of tertiary contacts. The information content is different from, and complementary to, the results of side-chain to side-chain crystal surveys and studies of helix-helix-crossing angles. Six geometry descriptors were recorded from each tertiary contact in nonredundant data sets of globular and transmembrane proteins. The descriptors included distances, angles, and dihedral angles that together describe completely the underlying geometry of each contact. From the results it is possible to identify differences in the geometry requirements of tertiary contacts between alpha-helices in general and transmembrane alpha-helices. The differences become more apparent when the correlation between the different geometry descriptors is analyzed. The results are compared with those of other types of secondary structure. Finally, an investigation of how the geometry of tertiary contacts changes with the amino-acid types involved in the contact is performed using multivariate techniques. The results of this study provide a well-defined overview of the underlying structural framework of tertiary contacts between alpha-helices, in both globular and TM environments, that will have valuable implications for predicting protein tertiary structure.

Amino Acid Sequence↗

PubMed2004

Assessment of multiple binding modes in ligand-protein docking.

Computational ligand-protein docking is routinely used for binding mode prediction. We have quantified the effect of considering multiple docking solutions on the success rate of obtaining the crystallographic binding mode. By selection of a small set of representatives, the experimentally observed binding mode can be predicted with a higher probability after a ligand-protein docking simulation. The proportion of correctly predicted complexes improved from 69% to 87% when five distinct binding modes were considered.

Crystallography, X-Ray↗

PubMed2004

Receptor flexibility in the in silico screening of reagents in the S1' pocket of human collagenase.

A major difficulty in structure-based molecular design is the prediction of the structure of the protein-ligand complex because of the enormous number of degrees of freedom. Commonly, the target protein is kept rigid in a single low-energy conformation. However, this does not reflect the dynamic nature of protein structures. In this work, we investigate the influence of receptor flexibility in virtual screening of reagents on a common scaffold in the S1' pocket of human collagenase (matrix metalloproteinase-1). We compare screening using a single-crystal structure and multiple NMR structures, both apo and holo forms. We also investigate two computational methods of addressing receptor flexibility that can be used when NMR data are not available. The results from virtual screening using the experimental structures are compared to those obtained using the two computational methods. From the results, we draw conclusions about the impact of target flexibility on the identification of active and diverse reagents in a virtual screening protocol.

Apoenzymes↗

PubMed2004

Ligand-protein docking using a quantum stochastic tunneling optimization method.

A novel hybrid optimization method called quantum stochastic tunneling has been recently introduced. Here, we report its implementation within a new docking program called EasyDock and a validation with the CCDC/Astex data set of ligand-protein complexes using the PLP score to represent the ligand-protein potential energy surface and ScreenScore to score the ligand-protein binding energies. When taking the top energy-ranked ligand binding mode pose, we were able to predict the correct crystallographic ligand binding mode in up to 75% of the cases. By using this novel optimization method run times for typical docking simulations are significantly shortened.

Algorithms↗

PubMed2004

Molecular modelling prediction of ligand binding site flexibility.

We have investigated the efficacy of generating multiple sidechain conformations using a rotamer library in order to find the experimentally observed ligand binding site conformation of a protein in the presence of a bound ligand. We made use of a recently published algorithm that performs an exhaustive conformational search using a rotamer library to enumerate all possible sidechain conformations in a binding site. This approach was applied to a dataset of proteins whose structures were determined by X-ray and NMR methods. All chosen proteins had two or more structures, generally involving different bound ligands. By taking one of these structures as a reference, we were able in most cases to successfully reproduce the experimentally determined conformations of the other structures, as well as to suggest alternative low-energy conformations of the binding site. In those few cases where this procedure failed, we observed that the bound ligand had induced a high-energy conformation of the binding site. These results suggest that for most proteins that exhibit limited backbone motion, ligands tend to bind to low energy conformations of their binding sites. Our results also reveal that it is possible in most cases to use a rotamer search-based approach to predict alternative low-energy protein binding site conformations that can be used by different ligands. This opens the possibility of incorporating alternative binding site conformations to improve the efficacy of docking and structure-based drug design algorithms.

Algorithms↗

PubMed2003

Efficient conformational sampling of local side-chain flexibility.

Side-chain flexibility of ligand-binding sites needs to be considered in the rational design of novel inhibitors. We have developed a method to generate conformational ensembles that efficiently sample local side-chain flexibility from a single crystal structure. The rotamer-based approach is tested here for the S1' pocket of human collagenase-1 (MMP-1), which is known to undergo conformational changes in multiple side-chains upon binding of certain inhibitors. First, a raw ensemble consisting of a large number of conformers of the S1' pocket was generated using an exhaustive search of rotamer combinations on a template crystal structure. A combination of principal component analysis and fuzzy clustering was then employed to successfully identify a core ensemble consisting of a low number of representatives from the raw ensemble. The core ensemble contained geometrically diverse conformers of stable nature, as indicated in several cases by a relative energy lower than that of the minimised template crystal structure. Through comparisons with X-ray crystallography and NMR structural data we show that the core ensemble occupied a conformational space similar to that observed under experimental conditions. The synthetic inhibitor RS-104966 is known to induce a conformational change in the side-chains of the S1' pocket of MMP-1 and could not be docked in the template crystal structure. However, the experimental binding mode was reproduced successfully using members of the core ensemble as the docking target, establishing the usefulness of the method in drug design.

Arginine↗