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P Greenidge

Publications and source records attributed to P Greenidge.

5 recordsLinked to original sources
PubMed2000

Functional probing of the human glucocorticoid receptor steroid-interacting surface by site-directed mutagenesis. Gln-642 plays an important role in steroid recognition and binding.

To elucidate which amino acids in the glucocorticoid receptor ligand-binding domain might be involved in determining steroid binding specificity by interaction with the D-ring of glucocorticoids, we have performed site-directed mutagenesis of the four amino acids Met-560, Met-639, Gln-642, and Thr-739 based on their proximity to the steroid in a model structure. Mutations of these residues affected steroid binding affinity, specificity, and/or steroid-dependent transactivation. The results indicate that these residues are located in close proximity to the ligand and appear to play a role in steroid recognition and/or transactivating sensitivity, possibly by changes in the steroid-dependent conformational change of this region, resulting in the formation of the AF-2 site. Mutation of Gln-642 resulted in a marked decrease in affinity for steroids containing a 17alpha-OH group. This effect was alleviated by the presence of a 16alpha-CH(3) group to a varying degree. Thr-739 appears to form a hydrogen bond with the 21-OH group of the steroid, as well as possibly forming hydrophobic interactions with the steroid. Met-560 and Met-639 appear to form hydrophobic interactions with the D-ring of the steroid, although the nature of these interactions cannot be characterized in more detail at this point.

Animals↗
PubMed1999

Valine 571 functions as a regional organizer in programming the glucocorticoid receptor for differential binding of glucocorticoids and mineralocorticoids.

The glucocorticoid receptor (GR) interacts specifically with glucocorticoids, whereas its closest relative, the mineralocorticoid receptor (MR), interacts with both glucocorticoids and mineralocorticoids, such as aldosterone. To investigate the mechanism underlying the glucocorticoid/mineralocorticoid specificity of the GR, we used a yeast model system to screen for GR ligand-binding domain mutants, substituted with MR residues in the segment 565-574, that can be efficiently activated by aldosterone. In all such increased activity mutants, valine 571 was replaced by methionine, even though most mutants also contained substitutions of other residues with their MR counterparts. Further analysis in yeast and COS-7 cells has revealed that the identity of residue 571 determines the behavior of other MR substituted residues in the 565-574 segment. Generally, MR substitutions in this region are only consistent with aldosterone binding if residue 571 is also replaced with methionine (MR conformation). If residue 571 is valine (GR conformation), most other MR substitution mutants drastically reduce interaction with both mineralocorticoid and glucocorticoid hormones. Based on these functional data, we hypothesize that residue 571 functions as a regional organizer involved in discriminating between glucocorticoid and mineralocorticoid hormones. We have used a molecular model of the GR ligand-binding domain in an attempt to interpret our functional data in structural terms.

Aldosterone↗
PubMed1997

Structure-activity relationships of cannabinoids: a joint CoMFA and pseudoreceptor modelling study.

A cannabinoid pseudoreceptor model for the CB1-receptor has been constructed for 31 cannabinoids using the molecular modelling software YAK. Additionally, two CoMFA studies were performed on these ligands, the first of which was conducted prior to the building of the pseudoreceptor. Its pharmacophore is identical with the initial superposition of ligands used for pseudoreceptor construction. In contrast, the ligand alignment for the second CoMFA study was taken directly from the final cannabinoid pseudoreceptor model. This altered alignment gives markedly improved cross-validated r2 values as compared to those obtained from the original alignment with r2 cross values of 0.79 and 0.63, respectively, for five components. However, the pharmacophore alignment has the better predictive ability. Both the CoMFA and pseudoreceptor methods predict the free energy of binding of test ligands well.

Cannabinoids↗
PubMed1996

Antimalarial activity: the search for marine-derived natural products with selective antimalarial activity.

In this short review, an approach to the isolation of potential antimalarial agents and lead compounds is outlined. A discussion of organism collection, followed by a description of biological testing and isolation methodologies, is also given. For two organisms, details of their secondary metabolite chemistry are reported. From one of these, Laurencia papillosa, the two aromatic compounds p-hydroxybenzaldehyde (1) and p-methoxybenzyl alcohol (2) were isolated. From the other, the tropical marine sponge Cymbastela hooperi, 15 diterpenes (3-17), which contain isonitrile, isothiocyanate, and isocyanate functionalities, are reported. Together with the diterpenes, three sesquiterpene hydrocarbons, 18-20, and the thiol, 21, were obtained. All structures were established by spectroscopic methods, particularly 1H-1H and 1H-13C shift-correlated 2D NMR spectroscopy and accurate mass measurement (HREIMS). The majority of isolates demonstrate significant and selective in vitro antimalarial activity. For compounds 4-17 a brief description of their possible structure-activity relationships is provided.

Animals↗