bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isosteric Replacement of A3 Val of Porcine Insulin by allo‐Thr
Authors: Li Moyi , Cui Dafu , Zhang Youshang 
Published: September 2003

AbstractA3 Val is important for insulin activity. It is invariant in insulins from different species studied thus far. Based on the three dimensional structure of insulin, it was thought to be involved in receptor binding. Its replacement by Leu resulted in remarkable lowering of insulin activity, indicating the crucial requirement of the side chain geometry at this position. When A3 Val was replaced by Thr, which is hydrophilic but isosteric with Val, substantial insulin activity was retained. Therefore, the isosteric requirement for receptor binding at this site is more stringent than the hydrophobic requirement. Here we report the replacement of A3 Val of porcine insulin by the unnatural allo‐Thr. The in vivo biological activity of A3 allo‐Thr insulin is similar to that of A3 Thr insulin or native insulin, but its receptor binding activity is 7.6% instead of 50% for A3 Thr insulin, indicating that at the A3 position the hydrophilic OH group of Thr could be more tolerated in receptor binding than the OH group of allo‐Thr. The retention of insulin activity by substituting A3 Val with the unnatural isosteric allo‐Thr demonstrates again the importance of isosteric interaction in the binding of insulin with its receptor.
The Structure and Function of Catalytic Domains Within Inositol Polyphosphate 5‐Phosphatases
Authors: Whisstock J. C. , Wiradjaja F. , Waters J. E. , Gurung R. 
Published: September 2003

AbstractPhosphoinositide signaling pathways regulate many essential cellular functions including proliferation, differentiation and survival, cytoskeletal organization, and vesicular trafficking. The inositol polyphosphate 5‐phosphatases regulate the cellular levels of several bioactive phosphoinositide species. This review describes the structure and function of the 5‐phosphatase and Sac1 catalytic domains of these enzymes. The crystal structure of the 5‐phosphatase domain has been solved and shares homology with members of the AP endonuclease family. The phosphoinositide polyphosphatase activity of the Sac1 domain, found in some inositol polyphosphate 5‐phosphatases, is defined by a motif, CX 5 R(T/S), also found in both protein and lipid phosphatases.
Structure and Function of Collagen‐Derived Endostatin Inhibitors of Angiogenesis
Authors: Sasaki Takako , Timpl Rupert , Hohenester Erhard 
Published: September 2003

AbstractEndostatins are inhibitors of endothelial cell migration and angiogenesis and have been shown to reduce tumor growth in animal models. They are derived from the nontriplehelical C ‐terminal NC1 domains of collagens XV and XVIII, which are released proteolytically in trimeric form and further converted to monomeric endostatins of about 20 kDa. Both endostatin isoforms share a compact globular fold, but differ in certain binding properties for proteins and cells, as well as in tissue distribution. Differences in activity were found between NC1 domains and endostatins and are related to the oligomerization state. Endostatin effects are not restricted to endothelial cells, but also control renal epithelial cells and neuronal guidance in C. elegans . Cellular receptors are still insufficiently characterized and include for endostatin‐XVIII heparan sulfate proteoglycans. Receptor engagement elicits various downstream effects including tyrosine kinase and gene activation. Much remains to be learned, however, about details of the signal transduction cascades and how they interfer with pro‐angiogenic factors under physiological conditions and during therapeutic treatment.
Structural Basis of Perturbed pKa Values of Catalytic Groups in Enzyme Active Sites
Authors: Harris Thomas K. , Turner George J. 
Published: September 2003

AbstractIn protein and RNA macromolecules, only a limited number of different side‐chain chemical groups are available to function as catalysts. The myriad of enzyme‐catalyzed reactions results from the ability of most of these groups to function either as nucleophilic, electrophilic, or general acid‐base catalysts, and the key to their adapted chemical function lies in their states of protonation. Ionization is determined by the intrinsic p K a of the group and the microenvironment created around the group by the protein or RNA structure, which perturbs its intrinsic p K a to its functional or apparent p K a . These p K a shifts result from interactions of the catalytic group with other fully or partially charged groups as well as the polarity or dielectric of the medium that surrounds it. The electrostatic interactions between ionizable groups found on the surface of macromolecules are weak and cause only slight p K a perturbations (<2 units). The sum of many of these weak electrostatic interactions helps contribute to the stability of native or folded macromolecules and their ligand complexes. However, the p K a values of catalytic groups that are found in the active sites of numerous enzymes are significantly more perturbed (>2 units) and are the subject of this review. The magnitudes of these p K a perturbations are analyzed with respect to the structural details of the active‐site microenvironment and the energetics of the reactions that they catalyze.
The Focal Adhesion Kinase‐‐A Regulator of Cell Migration and Invasion
Authors: Hauck Christof R. , Hsia Datsun A. , Schlaepfer David D. 
Published: September 2003

AbstractCell migration plays an important role in embryonic development, wound healing, immune responses, and in pathological phenomena such as tissue invasion and metastasis formation. In this review, we summarize recent reports that connect the focal adhesion kinase (FAK) to cell migration and invasion. FAK is a nonreceptor protein tyrosine kinase involved in signal transduction from integrin‐enriched focal adhesion sites that mediate cell contact with the extracellular matrix. Multiple protein‐protein interaction sites allow FAK to associate with adapter and structural proteins allowing for the modulation of mitogen‐activated protein (MAP) kinases, stress‐activated protein (SAP) kinases, and small GTPase activity. FAK‐enhanced signals have been shown to mediate the survival of anchorage‐dependent cells and are critical for efficient cell migration in response to growth factor receptor and integrin stimulation. Elevated expression of FAK in human tumors has been correlated with increased malignancy and invasiveness. Because recent findings show that FAK contributes to the secretion of matrix‐metalloproteinases, FAK may represent an important checkpoint in coordinating the dynamic processes of cell motility and extracellular matrix remodeling during tumor cell invasion.
Duchenne and Becker Muscular Dystrophy: From Gene Diagnosis to Molecular Therapy
Authors: Matsuo Masafumi 
Published: September 2003

AbstractDuchenne and Becker muscular dystrophy (DMD/BMD) are X‐linked muscular dystrophies. The isolation of the defective gene in DMD/BMD has led to a better understanding of the disease process and has promoted studies regarding the application of molecular therapy. The purpose of this review is to present the progress made in this area of research with particular reference to dystrophin Kobe. Based on the results from the molecular analysis of dystrophin Kobe, we propose a novel molecular therapeutic method for DMD in which antisense oligonucleotides transform DMD into a milder phenotype by inducing exon skipping. In addition, current proposals for the molecular therapy of DMD are discussed.
Synergistic Effect of Vitamin D Derivatives and Retinoids on C2C12 Skeletal Muscle Cells
Authors: Stio Maria , Celli Alessandra , Treves Cristina 
Published: September 2003

AbstractThe response of C 2 C 12 myoblasts to 1 nM 1,25‐dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ], two vitamin D analogues (KH 1060 and EB 1089, which are 20‐epi‐22‐oxa and 22,24‐diene‐analogues, respectively), 100 nM retinoids (9‐ cis retinoic acid, all‐ trans retinoic acid) and to combination treatments, after 72 h incubation, was studied. The incubation with 1,25(OH) 2 D 3 was ineffective on either cell proliferation or [ 3 H]thymidine incorporation (expressed as DPM per cell) or protein content per cell. On the contrary, all the other treatments inhibited cell proliferation, this inhibition being synergistic when the vitamin D derivatives were combined with 9‐ cis or all‐ trans retinoic acid, and increased [ 3 H]thymidine incorporation and protein content per cell. The levels of the VDR protein remarkably increased in comparison with control cells, except for the incubation with 9‐ cis retinoic acid. This increase was particularly accentuated in C 2 C 12 cells treated with KH 1060 and 9‐ cis retinoic acid in combination. These results, taken together, suggest a role for vitamin D derivatives and retinoids on C 2 C 12 cells.
Role of Ca2+‐Dependent Metalloprotease‐2 in Stimulating Ca2+ATPase Activity Under Peroxynitrite Treatment in Bovine Pulmonary Artery Smooth Muscle Membrane
Authors: Chakraborti Tapati , Das Sudip , Mandal Malay , Mandal Amritlal , Chakraborti Sajal 
Published: September 2003

AbstractWe have determined effect of the oxidant peroxynitrite (ONOO ‐) on Ca 2+ ‐dependent matrix metalloprotease‐2 (MMP‐2) activity and the role of the protease on Ca 2+ ATPase activity in bovine pulmonary vascular smooth muscle plasma membrane under ONOO ‐‐triggered conditions. The smooth muscle plasma membrane possesses a 72‐kDa protease activity in a gelatin‐containing zymogram. The 72‐kDa protease activity has been found to be inhibited by tissue inhibitor of metalloprotease‐2 (TIMP‐2), indicating that the protease is the matrix metalloprotease‐2 (MMP‐2). Treatment of the membrane suspension with ONOO ‐ caused stimulation of the MMP‐2 activity (as evidenced by 14 C‐gelatin degradation) and also increased Ca 2+ ATPase activity. The ONOO ‐‐triggered protease activity and the Ca 2+ ATPase activity were found to be inhibited by the antioxidants: vitamin E, thiourea, and mannitol. Pretreatment with catalase and superoxide dismutase did not significantly alter ONOO ‐‐stimulated MMP‐2 activity and Ca 2+ ATPase activity, indicating that peroxide and superoxide are not present in appreciable amount in ONOO ‐. Under both basal and ONOO ‐ triggered conditions, the MMP‐2 activity and the Ca 2+ ATPase activity were also inhibited by EGTA, 1:10‐phenanthroline, and TIMP‐2. However, the ONOO ‐‐stimulated MMP‐2 activity and the Ca 2+ ATPase activity were found to be insensitive to phenylmethylsulfonylfluoride, Bowman‐Birk inhibitor, chymostatin, leupeptin, antipain, N ‐ethylmaleimide, and pepstatin. These results suggest that ONOO ‐ caused stimulation of MMP‐2 activity and that the increased MMP‐2 activity subsequently played a pivotal role in stimulating Ca 2+ ATPase activity in bovine pulmonary vascular smooth muscle plasma membrane.
HIV Epidemics in Africa: What Explains the Variations in HIV Prevalence?
Authors: Buvé Anne 
Published: September 2003

AbstractThere are large differences in the prevalence of HIV infection between different regions in sub‐Saharan Africa, ranging from less than 10% in pregnant women in most of West Africa, to over 25% in pregnant women in large cities in Eastern and Southern Africa. These differences in HIV prevalence are in many instances due to differences in rate of spread of the virus. The multicenter study on factors determining the differential spread of HIV in four African cities tried to identify factors that could explain differences in spread of HIV between different regions in sub‐Saharan Africa. The study was conducted in four cities, including two cities with a relatively low HIV prevalence (Cotonou in Bénin and Yaoundé in Cameroon) and two cities with a high HIV prevalence (Kisumu in Kenya and Ndola in Zambia). The difference in HIV prevalence between the four cities could not be explained by differences in sexual behavior. Any differences in sexual behavior were outweighed by differences in factors that influence HIV transmission, i.e. male circumcision and HSV‐2 infection. These findings have important implications for the design of interventions.
Kaposi's Sarcoma Biology
Authors: Boshoff Chris 
Published: September 2003

AbstractCancer remains a major burden for HIV‐infected individuals. The majority of cancers associated with HIV infection are driven by oncogenic viruses like Epstein‐Barr virus, Kaposi's sarcoma‐associated herpesvirus and human papillomavirus. Kaposi's sarcoma is a tumour of endothelium and is the most common malignancy in HIV infected individuals. AIDS‐related cancers are providing critical insight into cancer immunity and viral oncogenesis.
The Development of HIV‐1 Subtype C Vaccines for Southern Africa
Authors: Williamson Anna‐Lise 
Published: September 2003

AbstractOne in nine people in South Africa are estimated to be HIV‐1 infected, with the majority of these infections being due to HIV‐1 subtype C. Until recently, most HIV‐1 candidate vaccines were not based on subtype C genes. In response to this epidemic, therefore, the South African AIDS Vaccine Initiative (SAAVI) was established to facilitate the development and testing of candidate HIV‐1 subtype C vaccines. The first HIV‐1 subtype C candidate vaccine is due to be tested at the end of 2002, and is based on Venezuelan encephalitis virus replicons expressing Gag protein. The next candidate vaccines to be tested will be DNA and modified vaccinia Ankara vaccines expressing subtype C genes.
Transcriptomics and Proteomics: Tools for the Identification of Novel Drug Targets and Vaccine Candidates for Tuberculosis
Authors: Betts Joanna C. 
Published: September 2003

AbstractThe availability of the complete genome sequence of Mycobacterium tuberculosis has revolutionised many areas of tuberculosis research and facilitated functional genomics studies. Most notably, transcriptomics and proteomics have become important tools in gaining increased understanding of the biology of M. tuberculosis and offer the promise of being able to deliver novel drug targets and vaccine candidates.
Molecular Epidemiology of TB: Challenging Dogmas and Asking New Questions
Authors: van Helden Paul D. 
Published: September 2003

AbstractTraditional epidemiological methods provide insight into the dynamics of diseases such as tuberculosis. These traditional techniques have limitations and rely on a number of assumptions. The application of molecular techniques to the study of epidemiology has allowed us to gain new insights into the biology of the organism Mycobacterium tuberculosis and the dynamics of the disease. We have been enabled to push the limits of understanding of the epidemiology of this disease, allowing us to challenge the old clinical dogmas, ask new questions, design new strategies, and measure the efficacy of such new interventions to combat this age‐old scourge. Among the dogmas challenged are that infection outside the home is commonplace, so‐called relapse cases may in fact be largely reinfection, and active transmission may be more common than previously thought and reactivation disease relatively uncommon. These findings alone demand urgent attention and the design of optimal intervention strategies to reduce the burden of disease.
A Chemical Approach Towards Understanding the Mechanism and Reversal of Drug Resistance in Plasmodium falciparum: Is it Viable?
Authors: Chibale Kelly 
Published: September 2003

AbstractGenetic and biochemical approaches to studies of drug resistance mechanisms in Plasmodium falciparum have raised controversies and contradictions over the past several years. A different and novel chemical approach to this important problem is desirable at this point in time. Recently, the molecular basis of drug resistance in P. falciparum has been associated with mutations in the resistance genes, Chloroquine Resistance Transporter (PfCRT) and the P‐glycoprotein homologue (Pgh1). Although not the determinant of chloroquine resistance in P. falciparum, mutations in Pgh1 have important implications for resistance to other antimalarial drugs. Because it is mutations in the aforementioned resistance genes rather than overexpression that has been associated with drug resistance in malaria, studies on mechanisms of drug resistance and its reversal by chemosensitisers should benefit from a chemical approach. Target‐oriented organic synthesis of chemosensitisers against proteins implicated in drug resistance in malaria should shed light on mechanism of drug resistance and its reversal in this area. The effect of structurally diverse chemosensitisers should be examined on several putative resistance genes in P. falciparum to deal with antimalarial drug resistance in the broadest sense. Therefore, generating random mutations of these resistance proteins and subsequent screening in search of a specific phenotype followed by a search for mutations and/or chemosensitisers that affect a specific drug resistance pathway might be a viable strategy. This diversity‐oriented organic synthesis approach should offer the means to simultaneously identify resistance proteins that can serve as targets for therapeutic intervention (therapeutic target validation) and chemosensitisers that modulate the functions of these proteins (chemical target validation).
Neutralizing Antibody Responses to HIV‐1 Infection
Authors: Morris Lynn 
Published: September 2003

AbstractNeutralizing antibodies represent an important component of immune control in many viral infections. In HIV‐1 infection, almost all individuals develop antibodies capable of neutralizing autologous viruses in vitro; however, the role of these antibodies in vivo still remains unclear. Their absence during the acute phase of infection, when the viral levels are brought under control, suggests they play a minor role in immune control and that cellular immune responses are more critical during this time. However, during chronic infection these antibodies may be important in preventing cell‐to‐cell spread and they still represent our best hope of providing sterilizing immunity (i.e., prevention of infection) by vaccination. Significant advances over the last few years in understanding the structure of the envelope glycoproteins have renewed interest in the role of neutralizing antibodies and the possibility that immunogens capable of stimulating a neutralizing antibody response can be developed.
Nutrient‐Gene Interactions in Mitochondrial Function: Vitamin A Needs Are Increased in BHE/Cdb Rats
Authors: Everts Helen B. , Berdanier Carolyn D. 
Published: September 2003

AbstractThe BHE/Cdb rat has a maternally inherited mutation in the ATPase 6 mitochondrial gene that associates with impaired oxidative phosphorylation (OXPHOS) and glucose intolerance. A longevity study revealed that feeding an egg‐rich (vitamin A‐rich) diet delayed the onset of impaired glucose tolerance. Two experiments were conducted to test the hypothesis that BHE/Cdb rats require more dietary vitamin A than normal rats. Experiment 1 was a dose‐response study examining OXPHOS in BHE/Cdb rats fed one of six levels of vitamin A. In experiment 2 BHE/Cdb and Sprague‐Dawley rats were used. The rats were depleted of retinol stores, then repleted with 4 or 12 IU vitamin A/g diet. Vitamin A status was assessed in depleted, never depleted, and depleted/repleted rats. OXPHOS was optimized at 4 IU/g diet for the Sprague‐Dawley rats and 12 IU/g diet for the BHE/Cdb rats. These results suggested that the criteria for vitamin intake adequacy in the BHE/Cdb rats is the optimization of mitochondrial OXPHOS. Using this criteria, we conclude that diabetes‐prone BHE/Cdb rats require more dietary vitamin A than normal rats.
Nutrient‐Gene Interactions: Dietary Vitamin A and Mitochondrial Gene Expression
Authors: Everts Helen B. , Claassen Daniel O. , Hermoyian Christina L. , Berdanier Carolyn D. 
Published: September 2003

AbstractThe BHE/Cdb rat is a model for mitochondrial diabetes due to a mutation in the ATPase 6 gene. These rats require more dietary vitamin A to optimize mitochondrial function than do normal Sprague‐Dawley rats. To determine a possible mechanism for this effect, cultured hepatocytes and hepatic tissues were studied. ATPase 6 (F 0 ATPase subunit a), retinoic acid receptors (RARs), and mitochondrial transcription factor A (mtTFA) gene products were determined using Western blot analysis. Northern analysis was used to determine ATPase 6, ATPase 6,8, and ND1 mRNA. Mitochondrial density was determined using confocal microscopy. Dose response studies using primary hepatocyte cultures showed that both ATPase 6 gene product and mRNA were optimized with additions of 10 ‐9 M retinoic acid. Retinoic acid receptors were found in the mitochondrial compartment. MtTFA levels were increased by vitamin A. Mitochondrial density was greater in the BHE/Cdb tissue than in Sprague‐Dawley tissue. These results show that vitamin A affects mitochondrial function via an effect on both nuclear and mitochondrial encoded genes.
Protease‐Activated Receptors: A Means of Converting Extracellular Proteolysis into Intracellular Signals
Authors: Mackie E. J. , Pagel C. N. , Smith R. , de Niese M. R. , Song S. ‐ J. , Pike R. N. 
Published: September 2003

AbstractProtease‐activated receptors (PARs) mediate cellular responses to a variety of extracellular proteases. The four known PARs constitute a subgroup of the family of seven‐transmembrane domain G protein‐coupled receptors and activate intracellular signalling pathways typical for this family of receptors. Activation of PARs involves proteolytic cleavage of the extracellular domain, resulting in formation of a new N terminus, which acts as a tethered ligand. PAR‐1, ‐3, and ‐4 are relatively selective for activation by thrombin whereas PAR‐2 is activated by a variety of proteases, including trypsin and tryptase. Recent studies in mice genetically incapable of expressing specific PARs have defined roles for PAR‐1 in vascular development, and for PAR‐3 and ‐4 in platelet activation, which plays a fundamental role in blood coagulation. PAR‐1 has also been implicated in a variety of other biological processes including inflammation, and brain and muscle development. Responses mediated by PAR‐2 include contraction of intestinal smooth muscle, epithelium‐dependent smooth muscle relaxation in the airways and vasculature, and potentiation of inflammatory responses. The area of PAR research is rapidly expanding our understanding of how cells communicate and control biological functions, in turn increasing our knowledge of disease processes and providing potential targets for therapeutic intervention.
What Nuclease Cleaves Pre‐mRNA in the Process of Polyadenylation?
Authors: Zarudnaya Margarita I. , Kolomiets Iryna M. , Hovorun Dmytro M. 
Published: September 2003

AbstractA transcript‐specific cleavage by a large set of proteins is the first stage of eukaryotic pre‐mRNA polyadenylation. The main participant of this reaction‐‐endonuclease‐‐has not been discovered until now. However, mammalian CPSF‐30 and yeast Yth 1p proteins are known to be homologues to Drosophila Clipper (CLP) protein, which possesses endoribonucleolytic activity. In the N ‐terminal region, all three proteins contain five copies of the CCCH zinc finger motif associated with nucleolytic activity in the case of CLP. The literature data on these proteins are reviewed here. These data were shown not to contradict the hypothesis that CPSF‐30 and its homologues are the actual nucleases that cleave pre‐mRNA in the process of polyadenylation.