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Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Ligand binding sites in proteins generally include "hot spots" that contribute a large fraction of the binding free energy and, therefore, are of prime interest in drug design. To find hot spots on the protein surface, a protein can be screened against libraries of small organic molecules to identify interaction sites using nuclear magnetic resonance (NMR) spectroscopy or the X-ray crystallographic technique Multiple Solvent Crystal Structures (MSCS). Small organic molecules can bind at several locations on the surface of a protein, but many different molecules congregate only in "consensus sites" identifying the hot spots. The mapping algorithm FTMAP is a computational analogue of experimental fragment screening methods. The principles of computational mapping were used for the development and testing of the binding site identification algorithm FTSITE, implemented as a web-based server. Finding ligand binding sites in silico is a classical challenge, and the success rate of identifying the ligand binding site as the first predicted site has increased to 83% during the last decade. FfSITE, based on biophysical modeling of protein-ligand interactions, increased the success rate to 94% on the same established test sets. Critical to the success of FfSITE is the use of multiple small molecules as probes; screening by X-ray crystallography and NMR spectroscopy had demonstrated a tendency of ligand binding sites to bind small organic compounds ranging 1n shapes, sizes, and polarities. Further, FfSITE does not use surrogate measures of ligand binding propensity such as site geometries and dimensions. It was shown that FTSITE can also successfully identify allosteric ligand binding sites that can serve as candidates for drug design. Furthermore, the hot spot information provided by FfMAP was shown to guide the development of core fragments, found by experimental fragment screening , into optimal ligands for a number of drug target proteins. Computational mapping can also be used for fragment-based drug design by finding fragments with preference for some regions of the binding site. To facilitate this analysis , a server enabling the fast generation of force field parameters for user-specified small molecules or fragments was developed. / 2999-01-01

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 146 p. : ill. Includes abstract. Includes bibliographical references.

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We have synthesized a new class of photoaffinity analogs, 2',3'-O-(2,4,6-trinitrophenyl)-8-azido-ATP, -ADP and -AMP (TNP- 8N₃ATP, -ADP and -AMP), and their radiolabeled derivatives, and characterized their interaction with the sarcoplasmic reticulum Ca²⁺-ATPase. The TNP-8N₃-nucleotides were synthesized from ATP in three steps involving bromination in the 8-position of the adenine ring followed by displacement with an azido group and then trinitrophenylation of the resulting 8N₃-nucleotide with TNBS. Inclusion of the oxidizing agent, DTNB, in the final reaction was found to be necessary to prevent reduction of the azido group by the released sulfite anion and also elevated the yield of trinitrophenylation to about 80%. Purity was determined spectrophotometrically, as well as by anion exchange TLC and reversed phase HPLC. In the dark, the compounds were found to display most of the features of the parent TNP-nucleotides and interacted with the Ca²⁺-ATPase in a similar way. When activated by illumination, the probes were specifically incorporated into SR vesicles with high efficiency at alkaline pH. The site of labeling was identified as being on the A₁ tryptic fragment.

Properties of the nucleotide binding site of the Ca²⁺-ATPase of skeletal muscle sarcoplasmic reticulum have been investigated. The study centred around interaction of the high affinity ATP analog, 2'-3'-0-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate, (TNP-ATP), with the Ca²⁺-ATPase. Defined fractions of the sarcoplasmic reticulum (SR), corresponding to the terminal cisternae (TC) and light SR (LSR), were isolated. The TC were shown to have distinctive morphological characteristics that differ from the LSR. The TC vesicles contained electron dense intravesicular material representative of Ca²⁺ binding proteins, and visible membranous "feet" structures, which are reported to interconnect with the transverse tubule. Functional characterisation of the isolated fractions provided evidence for the predominant localisation of Ca²⁺ release channels in TC, and concentration of Ca²⁺-ATPase molecules in LSR. These conclusions were based on the following observations: (a) decreased Ca²⁺ transport of TC versus LSR; ruthenium red, a Ca²⁺ channel blocker, enhanced Ca²⁺ transport and pumping efficiency in TC, (b) higher Ca²⁺-ATPase activity for LSR in the presence and absence of ionophore, (c) rapid Ca²⁺ efflux from TC which is inhibited by ruthenium red. Of special interest was the characterisation of the TC and LSR with respect to turnover-dependent TNP-ATP fluorescence. Fluorescence observed for TC was approximately 65% of that for LSR. This phenomenon may be attributable to either the decreased Ca²⁺ ATPase content of the TC vesicles or open Ca²⁺ release channels. Hence the TNP-ATP fluorescence characteristics appear to reflect the morphological and functional subspecialisation of the defined SR fractions.

The number of experimentally resolved protein structures in the Protein Data Bank has been growing fast in the last 20 years, which motivates the develop- ment of many computational tools for protein-ligand binding sites prediction. Binding sites prediction from protein 3D structure has many important applica- tions; it is an essential step in the complex process of rational drug design, it helps to infer the side-effects of drugs, it provides insight into proteins biological functions and it is helpful in many other fields, such as protein-ligand docking and molecular dynamics. As far as we know, there has not been a study that would systematically investigate general properties of known ligand binding sites on a large scale. In this thesis, we examine these properties using existing experimen- tal and predicted residue-level annotations of protein sequence and structure. We present an automated pipeline for statistical analysis of these annotations, based on hypothesis testing and effect size estimation. It is implemented in Python and it is easily extensible by user-defined annotations. The usage is demonstrated on 33 existing annotations and 4 different datasets. The practical significance of the results is tested with P2Rank prediction method. We hope that the results as well as the pipeline...

published_or_final_version / Biochemistry / Master / Master of Philosophy

The N-methyl-D-aspartate (NMDA) receptors are highly regulated ligand-gated ion channels, which are affected by many substrates. Overactivation of the NMDA receptor can lead to hyperexcitability and a number of neurotoxic effects and neurological diseases. Agmatine has been demonstrated to act allosterically as an inhibitory modulator at the polyamine recognition sites of the NMDA receptor complex. The present study synthesized and evaluated a library of agmatine analogs for their ability to displace tritiated MK-801 from NMDARs in P2 membrane preparations from rat brains at ligand concentrations of 1 mM and 50 uM. A full dose-response curve was generated for the most active compounds, in the presence and absence of a pathological level of spermidine (100 uM). A forty-five member subset of arylidenamino-guanidino compounds was synthesized and all were demonstrated to be NMDA receptor inhibitory modulators in the above assay. Three of these compounds generated biphasic curves, indicating activity at two binding sites: the postulated high-affinity agmatine binding site, and a low-affinity site (perhaps the channel itself). (4-Chlorobenzylidenamino)-guanidine hydrochloride demonstrated an IC50 of 3.6 uM at the former site and 124.5 uM at the latter. Several computer models were generated to direct further synthesis. Based on the structure-activity relationship of the arylidenamino-guanidino compounds, a pharmacophore model of the agmatine binding site of the NMDAR was proposed.

<p>RNA binding proteins (RBPs) and non-coding RNAs orchestrate gene expression in part through the recognition specific sites in mRNA. Thus understanding the connection between binding to specific sites and regulation of the whole transcript is essential. Current methods to do this can either identify the binding sites or quantitate binding to whole transcripts, but not both. Furthermore reliance of binding site detection on ultraviolet crosslinking results in inefficient identification of binding sites, and insufficient data to assess binding strength at sites. I have overcome these limitations by combining aspects of current methods to develop a new method called DO-RIP-seq (digestion optimization RNA immunoprecipitations with deep sequencing) that can quantitate the binding strength of RBPs at sites in mRNA, and also relate binding sites to binding of the whole mRNA. DO-RIP-seq was developed using the well-studied RBP ELAVL1/HuR as a test case, and applied to the less well-studied RBP known as RBM38/RNPC1. The quantitative data from DO-RIP-seq out-performed current binding site methods at predicting other features of the binding sites of HuR and RBM38, for example the lack of RNA secondary structure, and preferences in binding to particular sub-motifs. My studies indicate that DO-RIP-seq will be useful in uncovering the determinants of RNA-protein interactions, and studying dynamic biological processes that could modulate these interactions.</p> / Dissertation