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Paris G, Ramseyer C, Enescu M. A principal component analysis of the dynamics of subdomains and binding sites in human serum albumin. Biopolymers 2016; 101:561-72. [PMID: 24122695 DOI: 10.1002/bip.22418] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/23/2013] [Indexed: 01/05/2023]
Abstract
The conformational dynamics of human serum albumin (HSA) was investigated by principal component analysis (PCA) applied to three molecular dynamics trajectories of 200 ns each. The overlap of the essential subspaces spanned by the first 10 principal components (PC) of different trajectories was about 0.3 showing that the PCA based on a trajectory length of 200 ns is not completely convergent for this protein. The contributions of the relative motion of subdomains and of the subdomains (internal) distortion to the first 10 PCs were found to be comparable. Based on the distribution of the first 3 PC, 10 protein conformers are identified showing relative root mean square deviations (RMSD) between 2.3 and 4.6 Å. The main PCs are found to be delocalized over the whole protein structure indicating that the motions of different protein subdomains are coupled. This coupling is considered as being related to the allosteric effects observed upon ligand binding to HSA. On the other hand, the first PC of one of the three trajectories describes a conformational transition of the protein domain I that is close to that experimentally observed upon myristate binding. This is a theoretical support for the older hypothesis stating that changes of the protein onformation favorable to binding can precede the ligand complexation. A detailed all atoms PCA performed on the primary Sites 1 and 2 confirms the multiconformational character of the HSA binding sites as well as the significant coupling of their motions.
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Affiliation(s)
- Guillaume Paris
- Laboratoire Chrono Environnement UMR CNRS 6249, Faculté des Sciences et Techniques, La Bouloie, Université de Franche-Comté, 25030 Besançon cedex, France
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2
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Smalley JW, Olczak T. Heme acquisition mechanisms of Porphyromonas gingivalis - strategies used in a polymicrobial community in a heme-limited host environment. Mol Oral Microbiol 2016; 32:1-23. [PMID: 26662717 DOI: 10.1111/omi.12149] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2015] [Indexed: 01/14/2023]
Abstract
Porphyromonas gingivalis, a main etiologic agent and key pathogen responsible for initiation and progression of chronic periodontitis requires heme as a source of iron and protoporphyrin IX for its survival and the ability to establish an infection. Porphyromonas gingivalis is able to accumulate a defensive cell-surface heme-containing pigment in the form of μ-oxo bisheme. The main sources of heme for P. gingivalis in vivo are hemoproteins present in saliva, gingival crevicular fluid, and erythrocytes. To acquire heme, P. gingivalis uses several mechanisms. Among them, the best characterized are those employing hemagglutinins, hemolysins, and gingipains (Kgp, RgpA, RgpB), TonB-dependent outer-membrane receptors (HmuR, HusB, IhtA), and hemophore-like proteins (HmuY, HusA). Proteins involved in intracellular heme transport, storage, and processing are less well characterized (e.g. PgDps). Importantly, P. gingivalis may also use the heme acquisition systems of other bacteria to fulfill its own heme requirements. Porphyromonas gingivalis displays a novel paradigm for heme acquisition from hemoglobin, whereby the Fe(II)-containing oxyhemoglobin molecule must first be oxidized to methemoglobin to facilitate heme release. This process not only involves P. gingivalis arginine- and lysine-specific gingipains, but other proteases (e.g. interpain A from Prevotella intermedia) or pyocyanin produced by Pseudomonas aeruginosa. Porphyromonas gingivalis is then able to fully proteolyze the more susceptible methemoglobin substrate to release free heme or to wrest heme from it directly through the use of the HmuY hemophore.
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Affiliation(s)
- J W Smalley
- School of Dentistry, University of Liverpool, Liverpool, UK
| | - T Olczak
- Laboratory of Biochemistry, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
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Byrne DP, Manandhar SP, Potempa J, Smalley JW. Breakdown of albumin and haemalbumin by the cysteine protease interpain A, an albuminase of Prevotella intermedia. BMC Microbiol 2015; 15:185. [PMID: 26403890 PMCID: PMC4582931 DOI: 10.1186/s12866-015-0516-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 09/09/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Prevotella intermedia is a Gram-negative black-pigmenting oral anaerobe associated with periodontitis in humans, and has a haem requirement for growth, survival and virulence. It produces an iron porphyrin-containing pigment comprising monomeric iron (III) protoporphyrin IX (Fe(III)PPIX.OH; haematin). The bacterium expresses a 90-kDa cysteine protease termed interpain A (InpA) which both oxidizes and subsequently degrades haemoglobin, releasing haem. However, it is not known whether the enzyme may play a role in degrading other haem-carrying plasma proteins present in the gingival sulcus or periodontal pocket from which to derive haem. This study evaluated the ability of InpA to degrade apo- and haem-complexed albumin. RESULTS Albumin breakdown was examined over a range of pH and in the presence of reducing agent; conditions which prevail in sub- and supra-gingival plaque. InpA digested haemalbumin more efficiently than apoalbumin, especially under reducing conditions at pH 7.5. Under these conditions InpA was able to substantially degrade the albumin component of whole human plasma. CONCLUSIONS The data point to InpA as an efficient "albuminase" with the ability to degrade the minor fraction of haem-bound albumin in plasma. InpA may thus contribute significantly to haem acquisition by P. intermedia under conditions of low redox potential and higher pH in the inflamed gingival crevice and diseased periodontal pocket where haem availability is tightly controlled by the host.
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Affiliation(s)
- Dominic P Byrne
- Department of Biochemistry, Institute of Integrative Biology, The University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK.
| | - Surya P Manandhar
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, California, 90840, USA.
| | - Jan Potempa
- Malopolska Centre of Biotechnology and Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, Krakow, 30-387, Poland. .,Department of Oral Immunology and Infectious Diseases, University of Louisville School of Dentistry, 501 S. Preston St., Louisville, KY, 40202, USA.
| | - John W Smalley
- The University of Liverpool, School of Dentistry, Daulby Street, Liverpool, L69 3GN, UK.
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Artali R, Bombieri G, Calabi L, Del Pra A. A molecular dynamics study of human serum albumin binding sites. ACTA ACUST UNITED AC 2006; 60:485-95. [PMID: 15950224 DOI: 10.1016/j.farmac.2005.04.010] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Accepted: 04/04/2005] [Indexed: 11/22/2022]
Abstract
A 2.0 ns unrestrained Molecular Dynamics was used to elucidate the geometric and dynamic properties of the HSA binding sites. The structure is not stress affected and the rmsds calculated from the published crystallographic data are almost constant for all the simulation time, with an averaged value of 2.4A. The major variability is in the C-terminus region. The trajectory analysis of the IIA binding site put in evidence fast oscillations for the Cgamma@Leu203...Cgamma@Leu275 and Cgamma@Leu219...Cgamma@Leu260 distances, with fluctuations around 250 ps, 1000 ps and over for the first, while the second is smoothly increasing with the simulation time from 7 to 10A. These variations are consistent with a volume increase up to 20% confirmed by the inter-domain contacts analysis, in particular for the pair O@Pro148...Ogamma@Ser283, representing the change of distance between IB-h9 and IIA-h6, O@Glu149...Ogamma@Ser189 for sub-domains IB-h9/IIA-h1 and N@Val339...Odelta2@Asp447 sub-domains IIB-h9/IIIA-h1. These inter-domain motions confirm the flexibility of the unfatted HSA with possible binding site pre-formation.
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Affiliation(s)
- Roberto Artali
- Istituto di Chimica Farmaceutica e Tossicologica, Università di Milano, Viale Abruzzi 42, 20131 Milano, Italy.
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Decker M. Novel inhibitors of acetyl- and butyrylcholinesterase derived from the alkaloids dehydroevodiamine and rutaecarpine. Eur J Med Chem 2005; 40:305-13. [PMID: 15725500 DOI: 10.1016/j.ejmech.2004.12.003] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Revised: 12/02/2004] [Accepted: 12/02/2004] [Indexed: 11/19/2022]
Abstract
Derived from the structures of the alkaloids rutaecarpine and dehydroevodiamine (DHED), and the long-known acetylcholinesterase (AChE) inhibitor tacrine, respectively, novel compounds were synthesised, including: 13-methyl-5,8-dihydro-6H-isoquino[1,2-b]quinazolin-13-ium chloride (12), (8Z)-5,6-dihydro-8H-isoquino[1,2-b]quinazolin-8-imine (13), 5,8-dihydro-6H-isoquino[1,2-b]quinazoline (15a), 13-methyl-5,8-dihydro-6H-isoquino[1,2-b]quinazolin-13-ium chloride (16), 5,7,8,13-tetrahydroindolo [2',3':3,4]pyrido[2,1-b]quinazoline (17), and N-(2-phenylethyl)-N-[(12Z)-7,8,9,10-tetrahydroazepino [2,1-b]quinazolin-12(6H)-ylidene]amine (20), respectively. In a first step to evaluate their possible applicability for antiamnesic therapy, the inhibition of AChE and butyrylcholinesterase (BChE) were determined: compounds 13, 15a, 17, and 20 are moderate or strong inhibitors of ChE, the latter two compounds show a 10-fold higher affinity to BChE. Compound 12 is a moderate inhibitor of AChE showing selectivity towards this enzyme.
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Affiliation(s)
- Michael Decker
- Lehrstuhl für Pharmazeutische/Medizinische Chemie, Institut für Pharmazie, Friedrich-Schiller-Universität Jena, Philosophenweg 14, D-07743 Jena, Germany.
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Kratochwil NA, Huber W, Müller F, Kansy M, Gerber PR. Predicting plasma protein binding of drugs: a new approach. Biochem Pharmacol 2002; 64:1355-74. [PMID: 12392818 DOI: 10.1016/s0006-2952(02)01074-2] [Citation(s) in RCA: 402] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In spite of the large amount of plasma protein binding data for drugs, it is not obvious and there is no clear consensus among different disciplines how to deal with this parameter in multidimensional lead optimization strategies. In this work, we have made a comprehensive study on the importance of plasma protein binding and the influencing factors in order to get new insights for this molecular property. Our analysis of the distribution of percentage plasma protein binding among therapeutic drugs showed that no general rules for protein binding can be derived, except for the class of chemotherapeutics, where a clear trend towards lower binding could be observed. For the majority of indication areas, however, empirical rules are missing. We present here an extensive list of multiply determined primary association constants for binding to human serum albumin (HSA) for 138 compounds from the literature. Correlating these binding constants with the percentage fraction of protein bound showed that the percentage data above 90%, corresponding to a binding constant below 6 microM, are of insufficient accuracy. Furthermore, it could be demonstrated that the lipophilicity of drugs, traditionally felt to dominate binding to HSA, is not the only relevant descriptor. Here, we report a generic model for the prediction of drug association constants to HSA, which uses a pharmacophoric similarity concept and partial least square analysis (PLS) to construct a quantitative structure-activity relationship. It is able to single out the submicromolar to nanomolar binders, i.e. to differentiate between 99.0 and 99.99% plasma protein binding. Depending on the system, this can be important in medicinal chemistry programs and may together with other computed physicochemical and ADME properties assist in the prioritization of synthetic strategies.
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Fitos I, Visy J, Kardos J. Stereoselective kinetics of warfarin binding to human serum albumin: effect of an allosteric interaction. Chirality 2002; 14:442-8. [PMID: 11984760 DOI: 10.1002/chir.10113] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Kinetic and equilibrium binding studies were performed on the interaction of warfarin enantiomers with human serum albumin (HSA) in the absence and presence of lorazepam acetate (LoAc) enantiomers. Binding kinetics were followed by recording changes in the fluorescence of warfarin upon binding to HSA using the stopped-flow technique. The binding of (R)-warfarin displayed an exponentially increasing fluorescence, satisfying the two-step mechanism reported previously for the racemate, i.e., a diffusion controlled pre-equilibrium is followed by a slower rearrangement of the complex. In the case of (S)-warfarin, the signal was biphasic: a fast fluorescence enhancement was followed by a slow decline. The different kinetic features indicate that the equilibrium conformations of the [(S)-warfarin-HSA] and [(R)-warfarin-HSA] complexes are achieved via different mechanisms. The phenomenon was seen in buffers of different pH and compositions. Equilibrium binding measurements indicated significantly lower molar intrinsic fluorescence for the (S)-warfarin complex, suggesting differences in the microenvironments of the bound enantiomers. In the presence of (S)-LoAc, the allosterically enhanced binding of (S)-warfarin manifested itself in accelerated relaxation kinetics. In accordance with the low molar intrinsic fluorescence determined for the stable ternary complex, the amplitude of the decline in fluorescence became larger.
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Affiliation(s)
- Ilona Fitos
- Department of Molecular Pharmacology, Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
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Lund M, Bjerrum OJ, Bjerrum MJ. Structural heterogeneity of the binding sites of HSA for phenyl-groups and medium-chain fatty acids. Demonstration of equilibrium between different binding conformations. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 260:470-6. [PMID: 10095783 DOI: 10.1046/j.1432-1327.1999.00175.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A new facet of the very heterogeneous albumin molecule is described. Chromatography at pH 6-9 of human serum albumin (HSA) on a phenyl-sepharose column separates it into two nonconvertible conformations that are, in turn, in equilibrium with its binding and nonbinding forms. The hydrophobic interaction of HSA with phenyl-sepharose depends on ionic strength, pH, and time of contact with the immobilized ligand. Binding as a function of pH shows a minimum at pH 6.5, and the binding profile at pH 7-9 fits the titration of a weak monoprotic acid with a pKa of 7.3. There was no observable difference in the CD spectra or the masses of the two forms. The equilibrium between the albumin forms was examined under defined conditions and cannot be explained by a simple two-state model. Thus rechromatography of the nonbinding fraction derived from a sample in which 50% of the protein was originally retained resulted only in 10-20% bound protein. Correspondingly only 70-80% of the binding form was retained. A model explaining the observations can be derived if two species, I and II, exist in the solution, both being in an equilibrium with a binding and a nonbinding form, but in which I is not in equilibrium with II. The rate of conversion between the binding and nonbinding conformations was determined to be faster than 15 s at room temperature.
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Affiliation(s)
- M Lund
- Department of Chemistry, Royal Veterinary and Agricultural University, Frederiksberg, Denmark
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9
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Luik AI, Naboka YN, Mogilevich SM, Hushcha TO, Mishchenko NI. The influence of pH alteration and pharmacological modulators of adenylate cyclasie system on human serum albumin conformation. ACTA ACUST UNITED AC 1999. [DOI: 10.7124/bc.000500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- A. I. Luik
- Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine
| | - Yu. N. Naboka
- Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine
| | - S. M. Mogilevich
- Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine
| | - T. O. Hushcha
- Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine
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10
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Luik AI, Mogilevich SE, Hushcha TO, Mischenko NI. Study of human serum albumin structure by dynamic light scattering: two types of reactions under different pH and interaction with physiologically active compounds. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 1998; 54A:1503-1507. [PMID: 9807240 DOI: 10.1016/s1386-1425(98)00171-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effect of pH and binding of ten physiologically active compounds (isoproterenol, yohimbine, propranolol, clonidine, phenylephrine, carbachol, tripeptide fMLP, diphenhydramine, chlorpromazine and atropine) on the molecular structure of human serum albumin (HSA) has been studied using the dynamic light scattering. It was found that albumin globule has the most compact configuration (Stokes diameter 59-62 A) at physiological pH 7.4. The changes in pH, both increase to 8.0 and decrease to 5.4, result in the growth of globule size to 72-81 A. At acidic shift of pH an additional peak arises in the correlation spectra caused by the light scattering on the structures with the Stokes diameters of 29-37 A. Those conform to the sizes of the albumin subdomains. The indicated peak is not displayed at basic shift of pH. The interaction with propranolol, clonidine, phenylephrine, carbachol and tripeptide fMLP which hinder adenylate cyclase (AdC) and activate Ca-polyphosphoinositide (Ca-PPI) signaling system of a cell initiates structural rearrangements similar to acidic transitions. Isoproterenol, yohimbine diphenhydramine, chlorpromazine and atropine, which activate AdC and hinder Ca-PPI, cause conformational changes of HSA similar to basic transitions.
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11
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Luik AI, Naboka YN, Mogilevich SE, Hushcha TO, Mischenko NI. The influence of pH alteration and pharmacological modulators of adenylate cyclase system on human serum albumin conformation. J Biomol Struct Dyn 1998; 16:109-14. [PMID: 9745899 DOI: 10.1080/07391102.1998.10508231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The report describes the results of a study the effect of pH and binding of six physiologically active compounds (isoproterenol, yohimbine, theophylline, propranolol, clonidine and carbachol) on the molecular structure of human serum albumin (HSA) using dynamic light scattering. It was found that the albumin globule had the most compact configuration (Stokes diameter 59-62A) at physiological pH 7.4. The changes in pH both increased to 8.0 and decreased to 5.4, resulting in the growth of globule size to 72-81A. At acidic shift of pH an additional peak arose in the correlation spectra. This peak was caused by the light scattering on the structures with the Stokes diameters of 29-37A, which conformed to the sizes of the albumin subdomains. The additional peak was not displayed at basic shift of pH. The interaction with propranolol, clonidine and carbachol, which hinder adenylate cyclase (AdC) signaling system of a cell, initiated structural rearrangements similar to acidic transitions. Isoproterenol, yohimbine and theophylline, which activate AdC, caused the conformational changes of HSA similar to basic transitions.
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Affiliation(s)
- A I Luik
- Department of Biomedical Research, Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kyiv.
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12
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Ochoa de Aspuru E, Marquínez MA, Zatón AM. Protein dilution effect on thiouracil-seroalbumin interactions. Biophys Chem 1997; 69:233-7. [PMID: 9474756 DOI: 10.1016/s0301-4622(97)00094-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
As the spectra and binding parameters calculated for the thiouracil-albumin interaction change with the protein concentration, a human seroalbumin conformational change depending on protein concentration has been suggested. This protein-conformational change is tested by dilatometry and viscosimetry. At low concentrations, albumin showed a greater thiouracil binding capacity and a second positive peak in its interaction with the drug, detected by difference spectroscopy. Both effects are due to a monomerisation of protein dimers and not to a conformational change depending on protein concentration. This monomerisation would imply a major accessibility of thiouracil and propylthiouracil to other binding sites on HSA.
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Affiliation(s)
- E Ochoa de Aspuru
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Basque Country, Vitoria-Gasteiz, Spain
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13
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Smalley JW, Birss AJ. Albumin and hemalbumin degradation by Porphyromonas gingivalis. ORAL MICROBIOLOGY AND IMMUNOLOGY 1997; 12:254-8. [PMID: 9467396 DOI: 10.1111/j.1399-302x.1997.tb00388.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Degradation of bovine albumin and hemalbumin by Porphyromonas gingivalis W50 cells under non-reducing conditions at 37 degrees C was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and densitometry. Albumin and hemalbumins with heme:protein molar ratios of 1:1, 4:1 and 8:1 were degraded, yielding protease-resistant 55.6-kDa peptides. Cells of strains WPH 35, 11834 and Bg 381 also produced a similar digestion pattern. N-terminal sequencing of the 55.6-kDa albumin digestion fragment revealed two peptides with the sequences 82glu-thr-tyr-gly-asp-met-ala and 95gln-pro-glu-arg-asn-glu-cys, indicating cleavage in the N-terminal hinge region. Tosyllysylchloromethylketone and N-ethylmaleimide were the most effective in inhibiting breakdown of albumin and hemalbumin with a 1:1 heme:protein ratio. Initial degradation rates of albumin and all hemalbumins were similar, but the total amount of hemalbumins degraded over 7.5 h decreased with increased ratio of bound hemin. The specific proteolysis of hemalbumin may enable P. gingivalis to release hemin from a region of the molecule where heme binding is least avid.
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Affiliation(s)
- J W Smalley
- Department of Clinical Dental Sciences, University of Liverpool, United Kingdom
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Yamasaki K, Maruyama T, Kragh-Hansen U, Otagiri M. Characterization of site I on human serum albumin: concept about the structure of a drug binding site. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1295:147-57. [PMID: 8695640 DOI: 10.1016/0167-4838(96)00013-1] [Citation(s) in RCA: 191] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Human serum albumin (HSA) possesses at least three sites or areas for high-affinity binding of drugs. Of these sites, site I was investigated by series of ultrafiltration and equilibrium dialysis experiments. Three ligands, acenocoumarol, dansyl-L-asparagine (DNSA) and n-butyl p-aminobenzoate (n-butyl p-ABE) were employed as marker ligands. Each ligand binds to a single high-affinity site on HSA, and binding studies with different pairs of the ligands revealed independent high-affinity binding. Preliminary displacement studies performed with the typical site I binding drugs warfarin, phenylbutazone and iodipamide showed different displacement patterns of the three marker ligands. These studies were followed by stringent competition experiments involving all possible combinations of the three test ligands themselves and of these and the three marker ligands. On the basis of the results obtained it seems that the acenocoumarol and DNSA binding regions correspond to the warfarin and azapropazone binding regions, respectively, of site I reported by others (Fehske, Schläfer, Wollert and Müller (1982) Mol. Pharmacol. 21, 387-393). The new binding region, represented by n-butyl p-ABE, is probably located adjacent to the acenocoumarol binding region but apart from that of DNSA. We have elaborated a model for binding site I in which we propose novel nomenclatures, region Ia, Ib, and Ic for the acenocoumarol, DNSA and n-butyl p-ABE binding regions, respectively. Furthermore, the relation between these regions and the high-affinity binding sites for other drugs have been discussed.
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Affiliation(s)
- K Yamasaki
- Faculty of Pharmaceutical Sciences, Kumamoto University, Japan
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15
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Olson RE, Christ DD. Chapter 33. Plasma Protein Binding of Drugs. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1996. [DOI: 10.1016/s0065-7743(08)60472-8] [Citation(s) in RCA: 195] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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16
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Aki H, Yamamoto M. Thermodynamic characterization of drug binding to human serum albumin by isothermal titration microcalorimetry. J Pharm Sci 1994; 83:1712-6. [PMID: 7891299 DOI: 10.1002/jps.2600831213] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Binding sites on human serum albumin (HSA) for anionic drugs and fatty acids have been thermodynamically characterized by microcalorimetry. The binding and the thermodynamic parameters were directly computed from the calorimetric titration data at 37 degrees C in a phosphate buffer (pH 7.4) using one- and two-class binding models. From compensation analyses plotting the molar enthalpy change (delta Hm,i) versus those of the molar free energy (delta Gm,i) and molar entropy (delta Sm,i) for each class of binding sites, HSA binding sites were classified into groups S1, S2, and S3. Group S1 included high-affinity binding sites for site II-bound drugs, such as ibuprofen, flufenamic acid, and ethacrynic acid, and short- or medium-length alkyl-chain fatty acids; group S2 included low-affinity binding sites of site II-bound drugs and long-length alkyl-chain fatty acids; and group S3 contained the high-affinity binding sites for site I-bound drugs, such as phenylbutazone, oxphenbutazone, and warfarin, and long-length alkyl-chain fatty acids. High- and low-affinity bindings sites for salicylic acid and acetylaslicylic acid agreed with the regions of groups S3 and S2, respectively. Groups S1 and S2 were characterized by large negative values of delta Hm,i and delta Sm,i, reflecting van der Waals interaction and hydrogen-bonding formation in low dielectric media, and the main force to stabilize the binding complex in group S3 was a hydrophobic interaction, characterized by a small negative delta Hm,i and minor or positive values of delta Sm,i (entropy-driven).
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Affiliation(s)
- H Aki
- Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Fukuoka University, Japan
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