|PL||Prostacyclin and thromboxane synthases: Structural and functional characteristics|
Kenneth K. Wu, M.D., Ph.D.
National Health Research Institutes
Prostacyclin synthase (PGIS) and thromboxane synthase (TXAS) occupy a pivotal position in arachidonic acid metabolism. They catalyze the synthesis of two active molecules, PGI2 and TXA2, respectively, which play a critical role in vascular homeostasis and cardiovascular diseases. These two enzymes belong to cytochrome p450 (CYP) superfamily but are distinct from classic CYP in that they do not possess oxygenase activity. They function as isomerases that convert a common substrate PHG2 to PGI2 and TXA2, respectively. PGI2 and TXA2 have distinct chemical structures. It is of considerable interests to understand the catalytic mechanisms of these two enzymes. Our laboratory was the first to clone these two membrane proteins and characterize their structure-function relationship. We have also explored their roles in arachidonic acid metabolism and disease state by biochemical and molecular genetic approaches. In this talk, the structure-function, topology and function of these enzymes will be discussed.
Phyllotaxis and Leopard¡¦s spots
Department of Physics, National Chung-Hsing University
Nature is full of patterns. Their beauty is sometimes beyond human's imagination. One would agree that the shape of a rock, the pattern of cloud, and the orbit of a planet are governed by physical laws. However, it is to many people's surprise that shape and form of living creatures are also determined by physical laws, not by "natural selection". In this talk, I will discuss two examples, phyllotaxis of plants and coat pattern of the leopard, and show the plausibility of the physical models for determining biological forms.
|PL2||Mechanistic Studies of An Unusual C-O Bond Formation in Fosfomycin Biosynthesis|
Division of Medicinal Chemistry, College of Pharmacy,
The last step of the biosynthesis of fosfomycin is the conversion of (S)-2-hydroxypropylphosphonic acid (HPP) to fosfomycin. Since the ring oxygen in fosfomycin is derived from the hydroxyl group of HPP, this oxirane formation reaction is effectively a dehydrogenation process. To study this unusual C-O bond formation step, we have overexpressed and purified the desired HPP epoxidase. Our recent experiments showed that HPP epoxidase is an iron-dependent enzyme, and both NAD(P)H and a reductase are required for its activity. Although the identity of the reductase remains elusive, an iron-sulfur flavoprotein (E3) that mediates electron transfer in a deoxygenation reaction is capable of enhancing fosfomycin production. Interestingly, the flavin coenzyme (FMN/FAD) was also found to be an effective substitute for the putative reductase. While ether ring formation as a result of dehydrogenation of a secondary alcohol has precedence in the literature, these catalyses require £\-ketoglutarate for activity. In contrast, HPP epoxidase is £\-ketoglutarate independent. Thus, the cyclization of HPP to fosfomycin clearly represents an intriguing conversion beyond the scope entailed by common biological epoxidation and C-O bond formation. The X-ray structures of this enzyme, both alone and in complex with substrates, were recently determined. These structural data suggest how this enzyme is able to recognize its substrate and respond with a conformational change that protects the radical-based intermediates formed during catalysis. Further characterization of the iron core and elucidation of the mechanisms of the oxirane formation will be presented.
|PL3||NEUTRON DIFFRACTION NOW AND IN THE FUTURE: HOW IT WILL AFFECT BIOMOLECULAR RESEARCH|
Chemistry Department, University of Southern California, Los Angeles, CA 90089, U.S.A.
Single-crystal neutron diffraction data up to a resolution of 1.5 Å have been collected
at room temperature on two forms of rubredoxin using the BIX-3 diffractometer at the JRR-3 reactor of JAERI.
Rubredoxin is a small iron-sulfur redox protein with 53 amino acid residues, and the source of this particular protein
is the hyperthermophile Pyrococcus furiosus, a microorganism that normally lives at temperatures near that of
boiling water. Data were collected on crystals of the wild-type protein and on a mutant in which three of the residues
have been replaced. We were originally interested to see if the results of the neutron analysis would provide some
reasons to explain the remarkable thermal stability of the wild-type protein from this intriguing microorganism.
|PL4||Experiences of Molecular Images in Chang Gung Memorial University Hospital|
Tzu-Chen Yen, MD, PhD
Molecular Imaging Center and Department of Nuclear Medicine, Chang Gung Memorial Hospital and University
The Molecular Imaging Center (MIC) at Chang Gung Memorial Hospital at Linko was established
from June, 2006. The mission of this MIC was to establish a ¡§Translational Research Center¡¨. Under this mission,
the center has two parts. One is for early phase clinical trial and the other is for pre-clinical trial. For early phase
clinical trial, a 3T-MRI, a PET/CT, a cyclotron, a CGMP and more than 20 PIs are comprised. For pre-clinical trial,
a microPET, a microSPECT/microCT, an optic image, whole set instrumentations for autoradiography (two microtones,
a beta-imager and a phosphoimager) and qualified satellite animal room have been setup.
Research Center for Applied Sciences, Academia Sinica
Ellipsometric measurements coupled with efficient theoretical modeling are used to determine
the size, density, and distribution of various nanostructures on a multilayer film. Examples considered include metallic
nanospheres on a substrate and semiconductor nanorods. These samples were investigated by variable-angle spectroscopic
ellipsometry (VASE) in the ultraviolet to near infrared region (with wavelengths ranging from 140nm to 1100nm).
The spectroscopic ellipsometry measurements were carried out at several angles of incidence. It is found that the
results at 60o angle of incidence, which is close to the Brewster angle of the sample, show more distinct responses for
different samples. To understand the distribution of nanoparticles, rigorous coupled-wave analysis (RCWA)1 and
finite-element Green¡¦s function method2 were used to model the polarization-dependent reflectivity. Our model
calculations are in reasonable agreement with the ellipsometric measurements assuming the size distribution of
nanoparticels is uniform. Via the inverse scattering technique, we are also able to determine the average geometry of
semiconductor nanorods with resolution much smaller than the wavelength. This demonstrates that the spectroscopic
ellipsometry could be a useful tool to provide information about the size, shape and distribution of nanostructures on
a substrate or buried inside a multilayer film.
|PL6||Translational bioinformatics: a bioinformatics approach to discover the disease genes and mechanisms|
Bioinformatics Research Center, National Yang-Ming University
Disease is derived from a perturbation of normal regulation, which may lead to observable phenotypic changes. Since more and more diseases were found to be predisposed by genetic factors, the interaction of genes may play an important role in disease formation. By integrating the phenome with protein interaction network, the functional links of known risk factors can be revealed. We have taken advantage of this correlation to predict the candidate factors that may associate with diseases. On the other hand, studying the disease mechanism is more complicated, because different patients may have their unique way to develop the disease as a result of a specific gene-environment interaction. From another point of view, this complication may open a window for us to compare different disease states. Therefore, the process of disease formation and the regulatory circuit can be studied by comparing these states. By using the microarray data of each individual, it is possible to discover disease subtypes. An algorithm has been developed to discover the state-specific pathways. The disease-related pathways were first retrieved by using the Microarray Annotation and Profile (MAP) tool. The state-specific gene expression patterns were then mapped to known pathways. The function of pathways were annotated by gene ontology (GO). Therefore, the pathways can be classified by their functions in the cell. In the case of breast cancers, the IGFR and EGF pathways appear to be the predominant pathway for proliferation in estrogen receptor positive and negative subtypes, respectively. This observation was made by a pure informatics approach, but it was supported by wet laboratory experiments published previously. Taken together, these methods have successfully predicted phenomena that have been observed experimentally. Therefore, this strategy has the potential to analyze unknown phenomena in the future.
|PL7||Non-classical Pathway of Fibroblast Growth Factor Releasing|
Chemistry Department, National Tsing Hua University
Fibroblast growth factors (FGF) are key regulators of cell proliferation, differentiation and migration. They are crucial for early embryonic development, organ formation and angiogenesis. They also play important roles in tumor formation, inflammation, wound healing and restenosis. The biological functions of FGFs are mediated by a family of transmembrane tyrosine kinase receptors, FGFR. Thus to exert their activities, FGFs have to be released into the extracellular compartment. However, acidic FGF (FGF-1) and basic FGF (FGF-2), two prototypic members of the FGF family, which are represented in practically all tissues, lack the conventional amino-terminal signal sequence needed for the secretion of proteins through the classical endoplasmic reticulum (ER)-Golgi apparatus secretory pathway. Maciag et al. demonstrated that under cellular stress, FGF-1 is exported through a non-classical release pathway involving the formation of a specific copper (Cu2+)-dependent multiprotein complex. The protein constituents of this complex include the FGF-1 homodimer, the small calcium (Ca2+) binding protein, S100A13, and the p40 form of synaptotagmin 1 (Syt1), displaying two lipid binding domains, C2A and C2B, is a membrane docking protein which participates in exocytosis. The exact mechanism(s) by which the protein constituents specifically interact with each other and the molecular events which occur during the release of the multiprotein complex is still not clear. We propose a hypothetical model for the sequence of molecular events leading to the formation of the multiprotein release complex. The main aim of this proposal is to elucidate the molecular mechanism(s) underlying the non-classical export of FGF-1 through understanding the structure of the FGF-1 release complex.