Little is know about forskolin binding in the rat brain during ontogenetic development. For this paper, we have characterized specific binding sites for [3H]-forskolin in cerebrocortical membranes from young (12-day-old) and adult (90-day-old) rats. High-affinity, as well as super-high-affinity, [3H]-forskolin binding sites were detected in samples from both age groups tested, and the binding parameters of these sites differed significantly. Whereas the number of high-affinity [3H]-forskolin binding sites was higher by about 50% in adult than in young rats, their affinity was markedly (about 4 times) lower. In the presence of AlF4-, the number high-affinity [3H]-forskolin binding sites in samples from young rats rose to the level determined in samples from adult animals, and the number of super-high-affinity sites considerably increased in both age groups. The different characteristics of [3H]-forskolin binding found in cerebrocortical membranes from young and adult rats may be closely related to markedly diminished adenyl cyclase activity in preparations from adult animals. Results of our experiments with suramin indicated that this drug may act as a competitive inhibitor of [3H]-forskolin binding.

• MeSH
• agonisté adrenergních beta-receptorů farmakologie   MeSH
• baklofen farmakologie   MeSH
• buněčná membrána metabolismus   účinky léků   MeSH
• financování organizované MeSH
• GABA agonisté farmakologie   MeSH
• guanylylimidodifosfát farmakologie   MeSH
• hořčík farmakologie   MeSH
• isoprenalin farmakologie   MeSH
• kolforsin metabolismus   MeSH
• kompetitivní vazba účinky záření   MeSH
• krysa rodu rattus MeSH
• mozková kůra metabolismus   MeSH
• potkani Wistar MeSH
• receptory léků MeSH
• stárnutí metabolismus   MeSH
• suramin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH

INTRODUCTION: Competitive binding assays can be used to decipher not only the binding kinetics of studied ligands but also the binding site preference. Such assays are an essential step in the characterization of radioligands. However, the currently used competition assays require high concentrations of usually expensive ligands and still provide only binding site preference. By employing the time-resolved competition assay presented in this paper, binding characteristics including binding site preference can be obtained using less ligand. METHODS: To demonstrate the appropriateness of the time-resolved competition assay, we developed an assay in which the ligand binding was interrupted with a competitor. Experiments were performed on human carcinoma cell lines expressing epidermal growth factor receptor (EGFR). The targeting of the receptor was performed with radio-iodinated epidermal growth factor (EGF). The employed competitors involved either natural ligand transforming growth factor alpha (TGF-α) or anti-EGFR antibodies cetuximab and panitumumab targeting the same EGFR domain. RESULTS: Radio-iodinated EGF bound to EGFR was displaced with either low concentrations of cetuximab or high concentrations of panitumumab. In the case of TGF-α, we observed no competitive displacement of bound EGF at either high or low concentrations. When comparing the time-resolved competition assay with a manual competition assay, the resulting data of measured inhibition constants were in agreement. DISCUSSION: The results summarised in this study confirm the appropriateness of the time-resolved competition assay for assessing ligand binding properties. The assay has the potential to complement or replace conventional competition assays for determining binding site preference in the future.

• MeSH
• časové faktory MeSH
• epidermální růstový faktor chemie   metabolismus   MeSH
• erbB receptory antagonisté a inhibitory   chemie   metabolismus   MeSH
• humanizované monoklonální protilátky chemie   farmakologie   MeSH
• kompetitivní vazba účinky léků   MeSH
• lidé MeSH
• ligandy MeSH
• monoklonální protilátky chemie   farmakologie   MeSH
• nádorové buňky kultivované MeSH
• substrátová specifita MeSH
• transformující růstový faktor alfa chemie   metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

GHB (γ-hydroxybutyric acid) is a compound endogenous to mammalian brain with high structural resemblance to GABA. GHB possesses nanomolar-micromolar affinity for a unique population of binding sites, but the exact nature of these remains elusive. In this study we utilized the highly selective GHB analogue, 3-hydroxycyclopent-1-enecarboxylic acid (HOCPCA) as a tritiated version (3H-HOCPCA) to radioactively label the specific GHB high-affinity binding site and gain further insight into the density, distribution and developmental profile of this protein. We show that, in low nanomolar concentrations,3H-HOCPCA displays excellent signal-to-noise ratios using rodent brain autoradiography, which makes it a valuable ligand for anatomical quantification of native GHB binding site levels. Our data confirmed that3H-HOCPCA labels only the high-affinity specific GHB binding site, found in high density in cortical and hippocampal regions. The experiments revealed markedly stronger binding at pH 6.0 (Kd73.8 nM) compared to pH 7.4 (Kd2312 nM), as previously reported for other GHB radioligands but similar Bmaxvalues. Using3H-HOCPCA we analyzed the GHB binding protein profile during mouse brain development. Due to the high sensitivity of this radioligand, we were able to detect low levels of specific binding already at E15 in mouse brain, which increased progressively until adulthood. Collectively, we show that3H-HOCPCA is a highly sensitive radioligand, offering advantages over the commonly used radioligand3H-NCS-382, and thus a very suitable in vitro tool for qualitative and quantitative autoradiography of the GHB high-affinity site.

• MeSH
• autoradiografie metody   MeSH
• cyklopentany farmakologie   MeSH
• hlodavci MeSH
• hydroxybutyráty farmakologie   MeSH
• kompetitivní vazba MeSH
• kyseliny karboxylové farmakologie   MeSH
• mozek účinky léků   metabolismus   MeSH
• myši MeSH
• radioligandová zkouška metody   MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In nature, proteins have evolved sophisticated cavities tailored for capturing target guests selectively among competitors of similar size, shape, and charge. The fundamental principles guiding the molecular recognition, such as self-assembly and complementarity, have inspired the development of biomimetic receptors. In the current work, we report a self-assembled triple anion helicate (host 2) featuring a cavity resembling that of the choline-binding protein ChoX, as revealed by crystal and density functional theory (DFT)-optimized structures, which binds choline in a unique dual-site-binding mode. This similarity in structure leads to a similarly high selectivity of host 2 for choline over its derivatives, as demonstrated by the NMR and fluorescence competition experiments. Furthermore, host 2 is able to act as a fluorescence displacement sensor for discriminating choline, acetylcholine, L-carnitine, and glycine betaine effectively.The choline-binding protein ChoX exhibits a synergistic dual-site binding mode that allows it to discriminate choline over structural analogues. Here, the authors design a biomimetic triple anion helicate receptor whose selectivity for choline arises from a similar binding mechanism.

• MeSH
• acetylcholin chemie   metabolismus   MeSH
• bakteriální proteiny chemie   metabolismus   MeSH
• cholin chemie   metabolismus   MeSH
• fosfáty chemie   metabolismus   MeSH
• kinetika MeSH
• kompetitivní vazba MeSH
• krystalografie rentgenová MeSH
• membránové transportní proteiny chemie   metabolismus   MeSH
• molekulární modely MeSH
• proteinové domény * MeSH
• protonová magnetická rezonanční spektroskopie MeSH
• Sinorhizobium meliloti metabolismus   MeSH
• transportní proteiny chemie   metabolismus   MeSH
• vazba proteinů MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

The bilirubin (BR) photo-conversion in the human body is a protein-dependent process; an effective photo-isomerization of the potentially neurotoxic Z,Z-BR as well as its oxidation to biliverdin in the antioxidant redox cycle is possible only when BR is bound on serum albumin. We present a novel analytical concept in the study of linear tetrapyrroles metabolic processes based on an in-depth mapping of binding sites in the structure of human serum albumin (HSA). A combination of fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular modeling methods was used for recognition of the binding site for BR, its derivatives (mesobilirubin and bilirubin ditaurate), and the products of the photo-isomerization and oxidation (lumirubin, biliverdin, and xanthobilirubic acid) on HSA. The CD spectra and fluorescent quenching of the Trp-HSA were used to calculate the binding constants. The results of the CD displacement experiments performed with hemin were interpreted together with the findings of molecular docking performed on the pigment-HSA complexes. We estimated that Z,Z-BR and its metabolic products bind on two independent binding sites. Our findings support the existence of a reversible antioxidant redox cycle for BR and explain an additional pathway of the photo-isomerization process (increase of HSA binding capacity; the excess free [unbound] BR can be converted and also bound to HSA).

• MeSH
• bilirubin analogy a deriváty   chemie   metabolismus   MeSH
• biliverdin analogy a deriváty   chemie   metabolismus   MeSH
• cirkulární dichroismus MeSH
• fluorescenční spektrometrie MeSH
• fotochemické procesy * MeSH
• kompetitivní vazba MeSH
• lidé MeSH
• ligandy MeSH
• molekulární konformace MeSH
• molekulární modely * MeSH
• oxidace-redukce MeSH
• sérový albumin chemie   metabolismus   MeSH
• simulace molekulového dockingu MeSH
• stereoizomerie MeSH
• taurin analogy a deriváty   chemie   metabolismus   MeSH
• tryptofan chemie   MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The 14-3-3 protein family is a highly conserved and widely distributed group of proteins consisting of multiple isoforms in eukaryotes. Ubiquitously expressed, 14-3-3 proteins play key roles in DNA replication, cell cycle regulation, and apoptosis. The function of 14-3-3 proteins is mediated by interaction with a large number of other proteins and with DNA. It has been demonstrated that 14-3-3γ protein binds strongly to cruciform structures and is crucial for initiating replication. In this study, we analyzed DNA binding properties of the 14-3-3γ isoform to linear and supercoiled DNA. We demonstrate that 14-3-3γ protein binds strongly to long DNA targets, as evidenced by electrophoretic mobility shift assay on agarose gels. Binding of 14-3-3γ to DNA target results in the appearance of blurry, retarded DNA bands. Competition experiments with linear and supercoiled DNA on magnetic beads show very strong preference for supercoiled DNA. We also show by confocal microscopy that 14-3-3 protein in the HCT-116 cell line is co-localized with DNA cruciforms. This implies a role for the 14-3-3γ protein in its binding to local DNA structures which are stabilized by DNA supercoiling.

• MeSH
• Escherichia coli genetika   MeSH
• HCT116 buňky MeSH
• klonování DNA MeSH
• kompetitivní vazba MeSH
• křížová struktura DNA genetika   metabolismus   MeSH
• lidé MeSH
• plazmidy genetika   MeSH
• proteiny 14-3-3 genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny genetika   metabolismus   MeSH
• replikace DNA genetika   MeSH
• retardační test MeSH
• superhelikální DNA genetika   metabolismus   MeSH
• vazba proteinů MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Selective binding of the wild type tumor suppressor protein p53 to negatively and positively supercoiled (sc) DNA was studied using intercalative drugs chloroquine (CQ), ethidium bromide, acridine derivatives and doxorubicin as a modulators of the level of DNA supercoiling. The p53 was found to lose gradually its preferential binding to negatively scDNA with increasing concentrations of intercalators until the DNA negative superhelix turns were relaxed. Formation of positive superhelices (due to further increasing intercalator concentrations) rendered the circular duplex DNA to be preferentially bound by the p53 again. CQ at concentrations modulating the closed circular DNA topology did not prevent the p53 from recognizing a specific target sequence within topologically unconstrained linear DNA. Experiments with DNA topoisomer distributions differing in their superhelix densities revealed the p53 to bind selectively DNA molecules possessing higher number of negative or positive superturns. Possible modes of the p53 binding to the negatively or positively supercoiled DNA and tentative biological consequences are discussed.

• MeSH
• akridiny chemie   farmakologie   MeSH
• chlorochin chemie   farmakologie   MeSH
• doxorubicin chemie   farmakologie   MeSH
• interkalátory chemie   farmakologie   MeSH
• kompetitivní vazba MeSH
• konformace nukleové kyseliny účinky léků   MeSH
• lidé MeSH
• nádorový supresorový protein p53 chemie   metabolismus   MeSH
• superhelikální DNA chemie   účinky léků   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Of eight monoclonal antibodies raised against human transferrin, one (H.TF-14) cross reacted with pig and rabbit transferrins and one (H.TF-1) showed cross-reactivity with horse and dog transferrins. While rabbit and pig transferrins exhibited the same patterns of binding to MOLT-3 cell receptors as human and horse transferrins, binding of mouse and dog transferrins was weaker and bovine and carp transferrins gave entirely negative results. The results of these competitive binding experiments were confirmed by a biological test in which bovine transferrin had no effect on the growth of MOLT-3 cells when added to a serum-free medium. The observed correlation between cross-reactivity of anti-transferrin monoclonal antibodies and the binding abilities of transferrins to the MOLT-3 cell receptors may be associated with the conservatism of the part of the transferrin molecule recognized by the cell receptor.

• MeSH
• epitopy analýza   MeSH
• fylogeneze * MeSH
• kapři MeSH
• kompetitivní vazba MeSH
• koně MeSH
• králíci MeSH
• lidé MeSH
• monoklonální protilátky imunologie   MeSH
• ovce MeSH
• psi MeSH
• receptory buněčného povrchu metabolismus   MeSH
• receptory transferinu MeSH
• skot MeSH
• transferin imunologie   metabolismus   MeSH
• zkřížené reakce MeSH
• zvířata MeSH
• Check Tag
• králíci MeSH
• lidé MeSH
• psi MeSH
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Transient receptor potential channel vanilloid receptor subunit 1 (TRPV1) is a thermosensitive cation channel activated by noxious heat as well as a wide range of chemical stimuli. Although ATP by itself does not directly activate TRPV1, it was shown that intracellular ATP increases its activity by directly interacting with the Walker A motif residing on the C-terminus of TRPV1. In order to identify the amino acid residues that are essential for the binding of ATP to the TRPV1 channel, we performed the following point mutations of the Walker A motif: P732A, D733A, G734A, K735A, D736A, and D737A. Employing bulk fluorescence measurements, namely a TNP-ATP competition assay and FITC labelling and quenching experiments, we identified the key role of the K735 residue in the binding of the nucleotide. Experimental data was interpreted according to our molecular modelling simulations.

• MeSH
• adenosintrifosfát analogy a deriváty   chemie   MeSH
• chemické modely MeSH
• financování organizované MeSH
• kationtové kanály TRPV chemie   ultrastruktura   MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• počítačová simulace MeSH
• vazba proteinů MeSH
• vazebná místa MeSH

The Na+/K+-ATPase plays a key role in ion transport across the plasma membrane of all animal cells. The voltage-sensitive styrylpyrimidium dye RH421 has been used in several laboratories for monitoring of Na+/K+-ATPase kinetics. It is known, that RH421 can interact with the enzyme and it can influence its activity at micromolar concentrations, but structural details of this interaction are only poorly understood. Experiments with isolated large cytoplasmic loop (C45) of Na+/K+-ATPase revealed that RH421 can interact with this part of the protein with dissociation constant 1μM. The Trp-to-RH421 FRET performed on six single-tryptophan mutants revealed that RH421 binds directly into the ATP-binding site. This conclusion was further supported by results from molecular docking, site-directed mutagenesis and by competitive experiments using ATP. Experiments with C45/DPPC mixture revealed that RH421 can bind to both C45 and lipids, but only the former interaction was influenced by the presence of ATP.

• MeSH
• adenosintrifosfát metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• cytoplazma metabolismus   MeSH
• fluorescenční barviva metabolismus   MeSH
• kinetika MeSH
• mutageneze cílená metody   MeSH
• simulace molekulového dockingu MeSH
• sodíko-draslíková ATPasa metabolismus   MeSH
• tryptofan metabolismus   MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH