Thesis (Ph.D.)--Ohio University, August, 2005. / Includes bibliographical references (leaves 130-156)

Thesis (Ph. D.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: Ed Schmidt. Includes bibliographical references (leaves 88-107).

No description available.

A diafiltration technique was used to study drug-protein interactions. Fraction V human serum albumin and plasma and two drugs (phenylbutazone and bishydroxycoumarin) with a high affinity for these substances were used in this investigation. Preliminary experiments were carried out to check for release of foreign substances and for binding of drug to the Amicon diafiltration apparatus. A binding experiment, in the absence of drug, revealed release of a protein-like, ultraviolet absorbing substance from Fraction V human serum albumin. The most suitable method of purification for albumin was by diafiltration with Tris buffer. Binding curves for bishydroxycoumarin - human serum albumin, phenylbutazone - human serum albumin, and bishydroxycoumarin - plasma interactions were obtained. The r and r/Df [subscript omitted] values were calculated and binding parameters estimated by both graphical extrapolation and by a computer non-linear least squares fit analysis. Binding curves were not independent of human serum albumin concentration, but the cause of this effect was not fully resolved. Results showed the diafiltration technique can yield precise data, can be used over a wide macromolecule concentration range and produces a binding curve, from one experiment, over a wide range of molar binding ratios. Use of the Amicon diafiltration apparatus in desorption (washout) experiments and equilibrium or direct experiments was also investigated. Attempts were made to obtain binding data by centrifugation (ultrafiltration) and by a gel filtration technique (Sephadex G-25 batch method). These methods yielded unsatisfactory results which could not be compared with those obtained by diafiltration. This abstract represents the true contents of the thesis submitted. / Pharmaceutical Sciences, Faculty of / Graduate

An accurate plasma concentration-response relationship for propafenone (PF), a potent class 1 antiarrhythmic agent, has not yet been defined. A general pharmacological premise suggests that only the free drug is available to contribute to the observed pharmacological response. It has previously been shown that PF is highly bound to α-l-acid glycoprotein (AAG) which results in a low free PF concentration. The correlation of free PF concentration and response failed to adequately describe the dose response relationship. It has subsequently been shown that upon chronic dosing, two active metabolites, namely 5-hydroxypropafenone (5-OH-PF), and n-depropylpropafenone (n-depropyl-PF) accumulate in humans treated with PF. It is highly likely that the free concentration of PF, in addition to those of 5-OH-PF and n-depropyl-PF, contributes to the observed pharmacological effect following administration of PF at steady-state. To date, no accurate estimation of 5-OH-PF binding in serum has been established. This thesis examines the binding characteristics of PF and 5-OH-PF and their interaction in human serum, and in solutions of AAG, human serum albumin (HSA), high density lipoproteins (HDL), low density lipoproteins (LDL), and very low density lipoproteins (VLDL) using equilibrium dialysis. The binding of PF (2.0 μg/mL) and 5-OH-PF (0.5 μg/mL) was examined in serum when both drug and metabolite were present. The free fraction (FF) of PF and 5-OH-PF in serum was 0.063 ± 0.004 and 0.232 ± 0.020, respectively. Both PF and 5-0H-PF were found to bind to a high affinity, low capacity binding site on AAG, in addition PF showed a second low affinity, high capacity binding site. PF displayed a 10 fold greater affinity for the high affinity binding site on AAG when compared to 5-OH-PF. Both PF and 5-OH-PF showed only one low affinity, high capacity site on HSA of similar affinity. The interaction of PF and 5-OH-PF with HDL, LDL, and VLDL appeared to be due to solubilization, rather than a "true" drug-protein binding interaction, since it correlated well with the concentration of cholesterol within the lipoprotein complex (PF, r²=0.85; 5-OH-PF, r²=0.96). However, PF appeared to show saturable binding to the HDL complex. The uptake of PF and 5-OH-PF was greatest in LDL followed by HDL, and finally VLDL. In serum PF displayed both a high affinity, low capacity, and a low affinity, high capacity binding sites, although a similar observation was expected for 5-OH-PF, only one binding site could be experimentally identified. The uptake of 5-OH-PF by red blood cells (RBC) appeared to be approximately 5 fold greater than that of PF (i.e. The ratio of PF and 5-OH-PF concentration in the red blood cell/plasma was 0.7 ± 0.1 and 3.2 ± 0.5, respectively). When the binding of PF and 5-OH-PF was considered separately, the binding profiles were similar, that is, both drugs showed high affinity binding to AAG, and low affinity binding and/or non-specific binding to other serum proteins such as HSA, HDL, LDL, and VLDL. However, when both drug and metabolite were present, the binding of 5-OH-PF to AAG was found to be reduced. This is thought to occur as a result of the displacement of 5-OH-PF by PF from AAG. Thus, the binding of 5-OH-PF was noted to be more dependent on HSA, and lipoproteins when compared to PF. On the other hand, the binding of PF (2.0 μg/mL), even with the addition of 5-OH-PF, was dependent largely on the concentration of AAG. Although the binding of 5-OH-PF was apparently not altered by the addition of PF in serum, a decrease in the binding of 5-OH-PF by the addition of PF was observed. It is hoped that the understanding gained from this thesis will provide information regarding the relative importance of free PF and 5-OH-PF plasma concentration in future pharmacodynamic studies of PF. / Pharmaceutical Sciences, Faculty of / Graduate

Modification of cellular proteins with molecules of ubiquitin is an important process that regulates the activity of cellular proteins. Cullin RING ligases (CRLs) are multi-subunit complexes that act in concert with E2 enzymes to attach molecules of ubiquitin to protein substrates. There are seven CRLs in mammalian cells (Cul1, Cul2, Cul3, Cul4A, Cul4B, Cul5, and Cul7) that are highly homologous in sequence and structure. CRLs possess a highly conserved C- terminal domain that interacts with E2 enzymes, and a more variable N- terminal domain which recruits substrates through distinct substrate adapter molecules. Despite the structural similarity, these CRLs recognize distinct substrates and carry out unique functions in cells. In order to characterize the functional domains of cullins that are responsible for their unique activity, we generated cullin chimeras for expression and analysis in mammalian cells. These chimeras are Cul3 mutants in which the C- terminal domain or N- terminal domain of Cul3 has been replaced by that of Cul1 or Cul2, respectively. These chimeras were cloned into a mammalian expression vector for the purpose of experimentation in cultured cells. The chimeric cullin constructs provided a valuable tool for investigating how different functional domains of CRLs contribute to their specific functions in cells. In this study, we first investigated if the chimeras that we engineered were able to interact with their respective substrate adapters. We performed co- immunoprecipitation experiments in which we tested the ability of wild type, chimeric, or mutant cullin proteins to bind to three different substrate adapter proteins. We found that the chimera possessing the C- terminus of Cul1 and the N- terminus of Cul3 retains the ability to interact with the BTB substrate adapters Ctb57 and KLHL3. We also found that the chimera that possesses the C- terminus of Cul3 and the N- terminus of Cul1 was unable to interact with BTB proteins. Lastly, we found that the Cul1 adapter Skp1 was able to bind to Cul1, but did not bind to Cul3 or either chimera. We concluded that the chimera possessing the N- terminus of Cul3 likely retains the functional binding abilities of Cul3 at the N- terminus and would therefore be useful for conducting experiments. In this study, we also used the cullin chimeras to investigate the binding interactions between E2 enzymes and cullin RING ligases. We performed co- immunoprecipitation assays to examine the interactions between E2 enzymes and wild type, mutant or chimeric cullin proteins. We found that E2 enzyme UbE2E1 selectively binds to Cul3 and not to Cull. Notably, the BTB binding region at the N- terminus of Cul3 is required for binding to UbE2E1. Furthermore, we found that UbE2E1 also binds to Cul3 substrate adapter protein Ctb57. These experiments revealed a novel interaction between and E2 enzyme and the N- terminus of Cul3, as well as with a Cul3 substrate adapter protein. In conclusion, the chimeras generated in this study have provided valuable information regarding what regions of CRLs are important for interactions with other proteins, and will continue to be a useful tool for investigating CRL structure and function.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

No description available.

Viral RNA dependent RNA polymerases (RdRps) are enzymes which enable RNA viruses to replicate their genome and to prepare mRNA for translation of viral proteins. Due to its relative evolutionary conservation RdRps are good targets for drug design. In this work we present a structure of the RdRp (3Dpol ) of Aichi virus, which has not been solved yet. Aichi virus is a human pathogen that causes gastroenteritis. Aichi virus is also used as a model organism for studying cognate viruses which virulence is more dangerous, for example: Rhinovirus, Hepatitis A virus, SARS virus, hepatitis C virus, yellow fever, and West-Nile virus. In addition to structural studies of Aichi virus 3Dpol we also tested a previously published hypothesis that, 3Dpol is recruited to the membrane through phosphatidylinositol 4 phosphate (PI4P) - an important regulatory lipid. Membranes highly enriched in PI4P are formed in cells infected by single stranded positive sense RNA (plus ssRNA) viruses. Finally we tested the influence of ribonucleotides on the 3Dpol protein stability. (In Czech)