MyMedR

Displaying all 4 publications

Abstract:

Sort:

Molecular dynamics simulations of the adenosine A2a receptor: structural stability, sampling, and convergence

Ng HW, Laughton CA, Doughty SW

J Chem Inf Model, 2013 May 24;53(5):1168-78.
PMID: 23514445 DOI: 10.1021/ci300610w

Molecular dynamics (MD) simulations of membrane-embedded G-protein coupled receptors (GPCRs) have rapidly gained popularity among the molecular simulation community in recent years, a trend which has an obvious link to the tremendous pharmaceutical importance of this group of receptors and the increasing availability of crystal structures. In view of the widespread use of this technique, it is of fundamental importance to ensure the reliability and robustness of the methodologies so they yield valid results and enable sufficiently accurate predictions to be made. In this work, 200 ns simulations of the A2a adenosine receptor (A2a AR) have been produced and evaluated in the light of these requirements. The conformational dynamics of the target protein, as obtained from replicate simulations in both the presence and absence of an inverse agonist ligand (ZM241385), have been investigated and compared using principal component analysis (PCA). Results show that, on this time scale, convergence of the replicates is not readily evident and dependent on the types of the protein motions considered. Thus rates of inter- as opposed to intrahelical relaxation and sampling can be different. When studied individually, we find that helices III and IV have noticeably greater stability than helices I, II, V, VI, and VII in the apo form. The addition of the inverse agonist ligand greatly improves the stability of all helices.

Matched MeSH terms: Apoproteins/metabolism; Apoproteins/chemistry
Fulltext The conformational dynamics of H2-H3n and S2-H6 in gating ligand entry into the buried binding cavity of vitamin D receptor

Tee WV, Ripen AM, Mohamad SB

Sci Rep, 2016 Oct 27;6:35937.
PMID: 27786277 DOI: 10.1038/srep35937

Crystal structures of holo vitamin D receptor (VDR) revealed a canonical conformation in which the ligand is entrapped in a hydrophobic cavity buried in the ligand-binding domain (LBD). The mousetrap model postulates that helix 12 is positioned away from the domain to expose the interior cavity. However, the extended form of helix 12 is likely due to artifacts during crystallization. In this study, we set out to investigate conformational dynamics of apo VDR using molecular dynamics simulation on microsecond timescale. Here we show the neighboring backbones of helix 2-helix 3n and beta strand 2-helix 6 of LBD, instead of the helix 12, undergo large-scale motion, possibly gating the entrance of ligand to the ligand binding domain. Docking analysis to the simulated open structure of VDR with the estimated free energy of -37.0 kJ/mol, would emphasise the role of H2-H3n and S2-H6 in facilitating the entrance of calcitriol to the LBD of VDR.

Matched MeSH terms: Apoproteins/metabolism; Apoproteins/chemistry
Fulltext Crystal structure of Anoxybacillus α-amylase provides insights into maltose binding of a new glycosyl hydrolase subclass

Chai KP, Othman NF, Teh AH, Ho KL, Chan KG, Shamsir MS, et al.

Sci Rep, 2016 Mar 15;6:23126.
PMID: 26975884 DOI: 10.1038/srep23126

A new subfamily of glycosyl hydrolase family GH13 was recently proposed for α-amylases from Anoxybacillus species (ASKA and ADTA), Geobacillus thermoleovorans (GTA, Pizzo, and GtamyII), Bacillus aquimaris (BaqA), and 95 other putative protein homologues. To understand this new GH13 subfamily, we report crystal structures of truncated ASKA (TASKA). ASKA is a thermostable enzyme capable of producing high levels of maltose. Unlike GTA, biochemical analysis showed that Ca(2+) ion supplementation enhances the catalytic activities of ASKA and TASKA. The crystal structures reveal the presence of four Ca(2+) ion binding sites, with three of these binding sites are highly conserved among Anoxybacillus α-amylases. This work provides structural insights into this new GH13 subfamily both in the apo form and in complex with maltose. Furthermore, structural comparison of TASKA and GTA provides an overview of the conformational changes accompanying maltose binding at each subsite.

Matched MeSH terms: Apoproteins/chemistry
Inhibitory effect of phenethyl isothiocyanate against benzo[a] pyrene-induced rise in CYP1A1 mRNA and apoprotein levels as its chemopreventive properties

Abdull Razis AF, Konsue N, Ioannides C

Asian Pac J Cancer Prev, 2015;16(7):2679-83.
PMID: 25854346

BACKGROUND: Phenethyl isothiocyanate (PEITC), the most comprehensively studied aromatic isothiocyanate, has been shown to act as an anti-cancer agent mainly through modulation of biotransformation enzymes responsible for metabolizing carcinogens in the human body. Humans are often exposed to carcinogenic factors, some of which through the diet, such as polycyclic aromatic hydrocarbon benzo[a]pyrene via the consumption of over-cooked meats. Inhibition of the enzymes responsible for the bioactivation of this carcinogen, for example CYP1A1, the major enzyme required for polycyclic aromatic hydrocarbons (PAHs) bioactivation, is recognized as a chemoprevention strategy.
OBJECTIVE: To evaluate the inhibitory effects of PEITC against benzo[a]pyrene-induced rise in rat liver CYP1A1 mRNA and apoprotein levels.
MATERIALS AND METHODS: Precision cut rat liver slices were treated with benzo[a]pyrene at 1 and 5 μM in the presence of PEITC (1-25 μM) for 24 hours, followed by determination of CYP1A1 mRNA and apoprotein levels using quantitative polymerase chain reaction and immunoblotting.
RESULTS: Findings revealed that PEITC inhibited benzo[a]pyrene-induced rise in rat liver CYP1A1 mRNA in a dose-dependent manner as well as the apoprotein levels of CYP1A.
CONCLUSIONS: It was demonstrated that PEITC can directly inhibit the bioactivation of benzo[a]pyrene, indicating chemopreventive potential.

Matched MeSH terms: Apoproteins/metabolism*