Steroid sulfatase (STS) is considered to be one of the key enzymes contributing to the development of breast cancer. It catalyzes the hydrolysis of inactive sulfated steroids such as estrone sulfate (ES) to inorganic sulfate active steroids such as estrone (E1), a precursor to estradiol (E2), a key stimulator for breast cancer development. Inhibitors of STS are currently being pursued in both academia and industry as potential drugs for treating breast cancer. A series of 4-substituted estrone and estradiol derivatives were examined as inhibitors of STS. Inhibition of STS with 4-FE1, an irreversible inhibitor of STS previously studied in the Taylor group, can be enhanced by introducing a hydrophobic benzyl group at the 17-positon of 4-FE1. As with 4-FE1, the inhibition was concentration and time-dependent. Only 14% of the activity could be recovered after extensive dialysis. Introducing substituents at the 2-position of 4-formyl estrogen derivatives resulted in loss of concentration and time-dependent inhibition and a considerable decrease in inhibitor affinity. Studies with estrogen derivatives substituted at the 4-position with groups other than a formyl revealed that a relatively good reversible inhibitor can be obtained simply by introducing an electron withdrawing group at this position. These types of inhibitors are non-competitive inhibitors suggesting an alternative steroid binding site. A series of estrone derivatives were examined as photoaffinity labels of STS. 4-azidoestrone suflate and 4-azidoestrone phosphate exhibited properties that are suitable for photoaffinity labeling studies with STS. These labels may be useful for ascertaining pathways of substrate entry into the STS active site. 16-diazoestrone phosphate was not a photoaffinity label of STS. 2- and 4-azido estrone and 16-diazoestrone all acted as photoaffinity labels of STS. These compounds may be useful for ascertaining pathways of product release from the STS active site.

Steroid sulfatase (STS) is considered to be one of the key enzymes contributing to the development of breast cancer. It catalyzes the hydrolysis of inactive sulfated steroids such as estrone sulfate (ES) to inorganic sulfate active steroids such as estrone (E1), a precursor to estradiol (E2), a key stimulator for breast cancer development. Inhibitors of STS are currently being pursued in both academia and industry as potential drugs for treating breast cancer. A series of 4-substituted estrone and estradiol derivatives were examined as inhibitors of STS. Inhibition of STS with 4-FE1, an irreversible inhibitor of STS previously studied in the Taylor group, can be enhanced by introducing a hydrophobic benzyl group at the 17-positon of 4-FE1. As with 4-FE1, the inhibition was concentration and time-dependent. Only 14% of the activity could be recovered after extensive dialysis. Introducing substituents at the 2-position of 4-formyl estrogen derivatives resulted in loss of concentration and time-dependent inhibition and a considerable decrease in inhibitor affinity. Studies with estrogen derivatives substituted at the 4-position with groups other than a formyl revealed that a relatively good reversible inhibitor can be obtained simply by introducing an electron withdrawing group at this position. These types of inhibitors are non-competitive inhibitors suggesting an alternative steroid binding site. A series of estrone derivatives were examined as photoaffinity labels of STS. 4-azidoestrone suflate and 4-azidoestrone phosphate exhibited properties that are suitable for photoaffinity labeling studies with STS. These labels may be useful for ascertaining pathways of substrate entry into the STS active site. 16-diazoestrone phosphate was not a photoaffinity label of STS. 2- and 4-azido estrone and 16-diazoestrone all acted as photoaffinity labels of STS. These compounds may be useful for ascertaining pathways of product release from the STS active site.

The luteinizing hormone receptor (LHR) belongs to the G protein-coupled receptorfamily. It consists of two distinct domains; the N-terminal extracellular exodomain and themembrane associated endodomain which includes 7 transmembrane domains, 3 exoloops, 3cytoloops and a C-terminal tail. Sequence alignment and computer modeling suggest thepresence of Leu Rich Repeat (LRR) motifs in the exodomain. Although their structuralsimilarity is high, each LRR is not equally important for hormone binding. Ala-scanning andtruncation studies performed in our laboratory suggest that LRR2 and LRR4 appear to be themost crucial. The Ala-scanning data suggest that Leu103 and Ile105 in LRR4 are important forhormone binding. However, it is not clear whether these two residues make direct contact withhuman chorionic gonadotropin (hCG) or if they are necessary for the overall structural integrityof LRR4. In this work, the LHR peptide mimics of LRR4 were used for photoaffinity labeling todetermine whether Leu103 and Ile105 directly interact with hormone. Furthermore, LRR4peptides containing the photoactivable benzoylphenylalanine (Bpa) were used to determinewhether the LRR structure really exists in the LHR exodomain, whether LRR 4 interact withhCG, and which residues of LRR4 interact with hCG. Bpa was directly incorporated intodifferent positions of the LRR4 peptide sequence to examine the labeling ability of individualamino acids. The results suggest that LRR4, in particular the sequence of Lys101-Cys106,makes direct contact with hCG. However Leu103 and Ile105 do not interact with hCG but mayform the hydrophobic core of the LRR4 loop, which appears to be crucial for the LRR structure.Existing data suggest that glycoprotein hormones initially bind the exodomain. Thehormone/exodomain complex undergoes conformational adjustments and stimulates theendodomain of the receptor to generate hormone signals. The exoloops modulate hormonebinding and signaling; however, little is known about whether the hormone/exodomain complexcontacts the endodomain. To address this issue, we investigated whether the exoloops interactwith the hormone. First, we examined exoloop 3 that connects transmembrane domains 6 and 7which are important for signal generation. We present the first physical evidence that LHRexoloop 3 interacts with hCG.

No description available.

In an attempt to synthesize a photoreactive geranylcysteine derivative, A, with an appropriate photoprobe to be studied as a mimic for farnesylated protein, B, the following syntheses were carried out. The hydroxyl group of geraniol was protected with DHP/PPTs to generate 1 (98.1%). Allylic oxidation of 1 by using TBHP/SeO2 yielded 2 (31.5%). A modified oxidation increased the yield of 2 (34.4%). Treatment of 2 with BTC/pyridine afforded 3 (86.0%). Reaction of 3 with NaN3/DMF gave 8 and 9 (49.4%). Deprotection of this mixture under PPTs/EtOH afforded 10 and 11 (64.1%). Because of the unexpected reaction of 3 with N3-, we focused on alternative target molecules 12 and 13 (Figure 7). Our attempts to synthesize the first intermediates 14 and 15 in the syntheses of 12 and 13 (Scheme 14 and Scheme 15) have resulted in the isolation of the unreacted starting material.

No description available.

No description available.

Cytochromes P-450 (P450s) belong to haemoprotein superfamily and they are responsible for metabolism of a wide variety of compounds, among others many drugs and carcinogens. P450s serve as the terminal oxidases in the mixed function oxidase system in cooperation with a redox partner NADPH: cytochrome P450 reductase (CPR) providing input of two electrons to the reaction cycle of P450. The CPR can be substituted by other redox partner of P450, cytochrome b5 (cyt b5), to deliver the second electron. Three dimensional structure of P450 is required in order to fully understand its reaction mechanism. At the present time, a homology model of cytochrome P-450 2B4 (CYP 2B4) is available in our laboratory. In this study, the mapping of interaction domain between CYP 2B4 and cyt b5 employing a crosslinking agent EDC to form amide bonds between close complementary charged amino acid side chains was the first goal. We have identified five interacting amino acid pairs in total using mass spectrometry (MS). The second research interest was to verify and refine the CYP 2B4 model using a photoaffinity labelling with N-(p-azidobenzyl)-N-methyl-p-aminophenylamine probe. This photoreactive probe is known as CYP 2B4 ligand binding to the central iron atom of haem. After photoactivation the arginine 197 was found by MS...

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 174-185).

Thesis (Ph. D.)--Ohio State University, 2005. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2006 Nov 29