Development of a test system for inhibitors of human aldosterone synthase (CYP11B2): screening in fission yeast and evaluation of selectivity in V79 cells

Aldosterone synthase (CYP11B2) is a mitochondrial cytochrome P450 enzyme catalyzing the last steps of aldosterone production in the adrenal cortex. A new pharmacological approach for the treatment of the aldosterone induced effects in congestive heart failure and all forms of hyperaldosteronism could be the use of CYP11B2 inhibitors. In search for such compounds, it was our goal to develop a cellular enzyme assay suitable for screening high numbers of compounds. An assay procedure for the evaluation of inhibitors using the human CYP11B2 expressed in fission yeast Schizosaccharomyces pombe was established and a series of 10 compounds was tested in this whole cellular system. Human 11beta-hydroxylase (CYP11B1), which catalyzes the production of glucocorticoids, shows more than 90% homology compared to human CYP11B2. As this enzyme should not be affected, strong inhibitors of CYP11B2 have to be tested for selectivity. For that purpose, an assay procedure with V79MZ cells that express human CYP11B1 and CYP11B2, respectively, was integrated into the evaluation process. Using these screening procedures a potent and rather selective non-steroidal inhibitor of human CYP11B2 was detected with an IC(50) value of 59nM. We also identified a very potent inhibitor of both enzymes showing a stronger inhibitory activity against the cortisol producing CYP11B1.     

11C-MCG: synthesis,uptake selectivity,and primate PET of a probe for glutamate carboxypeptidase II (NAALADase)

Imaging of glutamate carboxypeptidase II (GCP II), also known as N-acetylated alpha-linked L-amino dipeptidase (NAALADase), may enable study of glutamatergic transmission, prostate cancer, and tumor neovasculature in vivo. Our goal was to develop a probe for GCP II for use with positron emission tomography (PET). Radiosynthesis of 11C-MeCys-C(O)-Glu or 11C-(S)-2-[3-((R)-1-carboxy-2-methylsulfanyl-ethyl)-ureido]-pentanedioic acid (11C-MCG), an asymmetric urea and potent (Ki = 1.9 nM) inhibitor of GCP II, was performed by C-11 methylation of the free thiol. Biodistribution of 11C-MCG was assayed in mice, and quantitative PET was performed in a baboon. 11C-MCG was obtained in 16% radiochemical yield at the end of synthesis with specific radioactivities over 167 GBq/mmol (4000 Ci/mmol) within 30 min after the end of bombardment. At 30 min postinjection, 11C-MCG showed 33.0 +/- 5.1%, 0.4 +/- 0.1%, and 1.1 +/- 0.2% ID/g in mouse kidney (target tissue), muscle, and blood, respectively. Little radioactivity gained access to the brain. Blockade with unlabeled MCG or 2-(phosphonomethyl)pentanedioic acid (PMPA), another potent inhibitor of GCP II, provided sevenfold and threefold reductions, respectively, in binding to target tissue. For PET, distribution volumes (DVs) were 1.38 then 0.87 pre- and postblocker (PMPA). Little metabolism of 11C-MCG occurred in the mouse or baboon. These results suggest that 11C-MCG may be useful for imaging GCP II in the periphery.     

Simultaneous determination of intact cisplatin and its metabolite monohydrated cisplatin in human plasma

Cisplatin is a cytotoxic platinum compound, used in the treatment of several solid tumors. Cisplatin and to a greater extent its hydrolysis product monohydrated cisplatin are responsible for side-effects like nephrotoxicity. A sensitive, accurate and precise method was developed to simultaneously determine cisplatin and monohydrated cisplatin in plasma. The compounds were separated by high-performance liquid chromatography and quantified by off-line furnace atomic absorption spectrophotometry. The linear ranges for cisplatin and monohydrated cisplatin in deproteinized plasma were 60-600 and 87.5-700 nM, respectively. From plasma, the mean recovery of cisplatin was 83.2% and that of monohydrated cisplatin 79.1%. The lower limits of quantification of cisplatin and monohydrated cisplatin in deproteinized plasma were 60 and 87.5 nM, respectively. Over the whole calibration range, the within- and between-day accuracy of intact cisplatin ranged from 100.7 to 111.4 and 94.8-102.0%, respectively. The within- and between-day accuracy of monohydrated cisplatin ranged from 107.1 to 113.3 and 101.4-104.9%, respectively. The within-day and between-day precision of cisplatin ranged from 3.4 to 11.5 and 7.3-10.3%, respectively. For monohydrated cisplatin, the within-day and between-day precision ranged from 3.7 to 6.2 and 5.6-7.9%, respectively. Currently, the developed assay has been implemented in pharmacokinetic studies of patients treated with cisplatin alone or in combination with other drugs.     

Retreat space and human visitor density moderate undesirable behavior in petting zoo animals

This study focused on the relationship between nonhuman animal behavior and environment-specifically, between the undesirable behavior exhibited by domestic petting zoo animals in the presence of humans and the spatial design of the petting zoo environment. A spatial feature of a petting zoo referred to as a retreat space was manipulated so that it affected the animals' opportunity for individual control over interaction with humans. Three conditions were tested: no retreat space, semi-retreat space, and a full-retreat space. The subjects of this study were 5 African pygmy goats (Capra hircus) and 2 Romanov sheep (Ovis aries). Investigators used a focal sampling technique to analyze approximately 27 hr of behavioral data collected. The data were analyzed using multiple linear regression methods. The findings suggest that the full-retreat design beneficially moderated both sheep and goat behavior: Undesirable behaviors were lowest in the full-retreat condition. This study provides information that may improve human-animal interactions in a petting zoo setting and may increase animal well-being through exhibit design and management techniques.     

Domain-specific antibodies reveal multiple-site topology of Nup153 within the nuclear pore complex

Nup153, one of the best characterized nuclear pore complex proteins (nucleoporins), plays a critical role in the import of proteins into the nucleus as well as in the export of RNAs and proteins from the nucleus. Initially an epitope of Nup153 was found to reside at the distal ring of the NPC, whereas more recently another epitope was localized to the nuclear ring moiety of the NPC. In an effort to more definitively determine the location of Nup153 within the 3-D architecture of the NPC we have generated domain-specific antibodies against distinct domains of Xenopus Nup153. With this approach we have found that the N-terminal domain is exposed at the nuclear ring of the NPC, whereas the zinc-finger domain of Nup153 is exposed at the distal ring of the NPC. In contrast, the C-terminal domain of Nup153 is not restricted to one particular subdomain of the NPC but rather appears to be highly flexible. Exogenous epitope-tagged hNup153 incorporated into Xenopus oocyte NPCs further underscored these findings. Our data illustrate that multiple domain-specific antibodies are essential to understanding the topology of a nucleoporin within the context of the NPC. Moreover, this approach has revealed new clues to the mechanisms by which Nup153 may contribute to nucleocytoplasmic transport.     

Alternans and 2:1 rhythms in an ionic model of heart cells

ECG alternans is commonly held to be an indicator of electrical instability of the heart, but the development of alternans has not yet been fully understood theoretically. We investigate the onset of alternans and 2:1 rhythms for stimulation at increasing frequencies in the Beeler-Reuter model, a simple ionic model of cardiac tissue. We find hysteresis and bistability at the onset of alternans; well-timed stimuli can switch between the two limit cycles. We determine quantitatively the effect of blocking specific ionic currents. Moreover, we find that calcium buffers generally promote alternans.     

Interactions between heme d and heme b595 in quinol oxidase bd from Escherichia coli: a photoselection study using femtosecond spectroscopy

Femtosecond spectroscopy was performed on CO-liganded (fully reduced and mixed-valence states) and O(2)-liganded quinol oxidase bd from Escherichia coli. Substantial polarization effects, unprecedented for optical studies of heme proteins, were observed in the CO photodissociation spectra, implying interactions between heme d (the chlorin ligand binding site) and the close-lying heme b(595) on the picosecond time scale; this general result is fully consistent with previous work [Vos, M. H., Borisov, V. B., Liebl, U., Martin, J.-L., and Konstantinov, A. A. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 1554-1559]. Analysis of the data obtained under isotropic and anisotropic polarization conditions and additional flash photolysis nanosecond experiments on a mutant of cytochrome bd mostly lacking heme b(595) allow to attribute the features in the well-known but unusual CO dissociation spectrum of cytochrome bd to individual heme d and heme b(595) transitions. This renders it possible to compare the spectra of CO dissociation from reduced and mixed-valence cytochrome bd under static conditions and on a picosecond time scale in much more detail than previously possible. CO binding/dissociation from heme d is shown to perturb ferrous heme b(595), causing induction/loss of an absorption band centered at 435 nm. In addition, the CO photodissociation-induced absorption changes at 50 ps reveal a bathochromic shift of ferrous heme b(595) relative to the static spectrum. No evidence for transient binding of CO to heme b(595) after dissociation from heme d is found in the picosecond time range. The yield of CO photodissociation from heme d on a time scale of < 15 ps is found to be diminished more than 3-fold when heme b(595) is oxidized rather than reduced. In contrast to other known heme proteins, molecular oxygen cannot be photodissociated from the mixed-valence cytochrome bd at all, indicating a unique structural and electronic configuration of the diheme active site in the enzyme.     

Structure-based functional inference in structural genomics

The dramatically increasing number of new protein sequences arising from genomics 4 proteomics requires the need for methods to rapidly and reliably infer the molecular and cellular functions of these proteins. One such approach, structural genomics, aims to delineate the total repertoire of protein folds in nature, thereby providing three-dimensional folding patterns for all proteins and to infer molecular functions of the proteins based on the combined information of structures and sequences. The goal of obtaining protein structures on a genomic scale has motivated the development of high throughput technologies and protocols for macromolecular structure determination that have begun to produce structures at a greater rate than previously possible. These new structures have revealed many unexpected functional inferences and evolutionary relationships that were hidden at the sequence level. Here, we present samples of structures determined at Berkeley Structural Genomics Center and collaborators laboratories to illustrate how structural information provides and complements sequence information to deduce the functional inferences of proteins with unknown molecular functions.Two of the major premises of structural genomics are to discover a complete repertoire of protein folds in nature and to find molecular functions of the proteins whose functions are not predicted from sequence comparison alone. To achieve these objectives on a genomic scale, new methods, protocols, and technologies need to be developed by multi-institutional collaborations worldwide. As part of this effort, the Protein Structure Initiative has been launched in the United States (PSI; www.nigms.nih.gov/funding/psi.html). Although infrastructure building and technology development are still the main focus of structural genomics programs [1–6], a considerable number of protein structures have already been produced, some of them coming directly out of semi-automated structure determination pipelines [6–10]. The Berkeley Structural Genomics Center (BSGC) has focused on the proteins of Mycoplasma or their homologues from other organisms as its structural genomics targets because of the minimal genome size of the Mycoplasmas as well as their relevance to human and animal pathogenicity (http://www.strgen.org). Here we present several protein examples encompassing a spectrum of functional inferences obtainable from their three-dimensional structures in five situations, where the inferences are new and testable, and are not predictable from protein sequence information alone.     

Secondary metabolites from the liverwort Jamesoniella colorata

Six new labdane type diterpenoids, three seco-clerodane diterpenoids, jamesoniellide I, along with the two new jamesoniellides K and L, the sesquiterpene waitziacuminone and a new chlorinated bisbibenzyl, 6,6',10,10',12,12'-hexachloroisoperrottetin A, have been isolated from the liverwort Jamesoniella colorata. Their structures were elucidated by NMR spectroscopy. The absolute configuration of 3-oxo-labda-8(17),13(16),14-triene (1) was established by CD spectroscopy.