An unusual orientation for Tyr75 in the active site of the aspartic proteinase from Saccharomyces cerevisiae

The structures of the native Saccharomyces cerevisiae proteinase A have been solved by molecular replacement in the monoclinic and trigonal crystal forms and refined at 2.6-2.7A resolution. These structures agree overall with those of other uninhibited aspartic proteinases. However, an unusual orientation for the side chain of Tyr75, a conserved residue on the flexible "flap" that covers the active site and is important for the activity of these enzymes, was found in the trigonal crystals. A similar conformation of Tyr75 occupying the S1 substrate-binding pocket was previously reported only for chymosin (where it was interpreted as representing a "self-inhibited" state of the enzyme), but for no other aspartic proteinases. Since this orientation of Tyr75 has now been seen in the structures of two members of the family of aspartic proteinases, it might indicate that the placement of that residue in the S1 substrate-binding pocket might have some functional significance, analogous to what was seen for self-inhibited structures of serine proteinases.     

The Pco proteins are involved in periplasmic copper handling in Escherichia coli

The interactions between the plasmid-borne copper resistance determinant, pco, and the main copper export system in Escherichia coli have been investigated and no direct interaction has been found. The PcoE and PcoC proteins are periplasmic and PcoC binds one Cu ion per protein molecule. PcoA is also periplasmic and can substitute for the chromosomally encoded CueO protein. The pco determinant is proposed to exert its effect through periplasmic handling of excess copper ions and to increase the level of resistance to copper ions above that conferred by copA alone.     

Crystal structure of the BAFF-BAFF-R complex and its implications for receptor activation

B-cell activating factor (BAFF) is a key regulator of B-lymphocyte development. Its biological role is mediated by the specific receptors BCMA, TACI and BAFF-R. We have determined the crystal structure of the extracellular domain of BAFF-R bound to BAFF at a resolution of 3.3 A. The cysteine-rich domain (CRD) of the BAFF-R extracellular domain adopts a beta-hairpin structure and binds to the virus-like BAFF cage in a 1:1 molar ratio. The conserved DxL motif of BAFF-R is located on the tip of the beta-turn and is indispensable in the binding of BAFF. The crystal structure shows that a unique dimeric contact occurs between the BAFF-R monomers in the virus-like cage complex. The extracellular domain of TACI contains two CRDs, both of which contain the DxL motif. Modeling of TACI-BAFF complex suggests that both CDRs simultaneously interact with the BAFF dimer in the virus-like cage.     

Detection of substance P and its mRNA in human blast cells in childhood lymphoblastic leukaemia using immunocytochemistry and in situ hybridisation

The study focused on determining the expression of substance P (SP) in neoplastic cells of childhood acute lymphoblastic leukaemia (ALL) at the levels of its mRNA and the protein production. The study group comprised 44 children treated for ALL in the Department of Paediatric Haematology and Oncology, Karol Marcinkowski University of Medical Sciences in Poznań, in the years 1999-2001. Bone marrow smears were obtained by needle biopsy. Expression of SP was examined by immunocytochemistry with specific antibody against human SP and by in situ hybridisation with anti-mRNA 5'-biotinylated probe. The results of the study demonstrated that SP could be detected in the cytoplasm of lymphoblasts (mean percentage of 81.8% for immunocytochemical and 84.5% for in situ hybridisation technique) in leukaemias of the common and T-cell types. SP was absent from blasts in B-cell leukaemia and from normal haematopoietic, cells in children of the control group. The results show that lymphoblasts of common and T-cell origin acquire the capability to synthesise SP after their neoplastic transformation in childhood acute leukaemia. SP may be involved in auto- and paracrine mechanisms capable of inducing hyperplasia of the neoplastic cells.     

Effect of resistant starch from corn or rice on glucose control,colonic events,and blood lipid concentrations in streptozotocin-induced diabetic rats

To examine the effect of two types of resistant starch on blood glucose and insulin levels, colonic events, hypolipidemic actions and humoral immune responses, Sprague-Dawley streptozotocin-induced diabetic rats were fed diet containing resistant starch from corn or rice. The marked body weight loss by inducing diabetes was not recovered by feeding resistant starch, even though there are no differences in food intakes compared to the non-diabetic control rats. No significant effect of resistant starch feeding on blood glucose and insulin was found. Even though the length of small intestines, and cecum, colon and rectum together with the tissue weight of cecum were not affected by feeding resistant starch, the intestinal transit time was markedly shortened by both types of resistant starch and resistant starch from corn had a more pronounced effect. The short chain fatty acids in the intestinal contents did not appear to be different among the groups. Nonetheless, both of resistant starch from corn and rice significantly lowered plasma total lipid and cholesterol concentrations compared to the diabetic control. The total liver cholesterol lowering effect was observed with resistant starch from rice. Neither immunoglobulin G nor C(3) were influenced by resistant starch.     

Role of Reactive Oxygen Species and Glutathione in Inorganic Mercury-Induced Injury in Human Glioma Cells

The present study was undertaken to examine the role of reactive oxygen species (ROS) and glutathione (GSH) in glia cells using human glioma cell line A172 cells. HgCl₂ caused the loss of cell viability in a dose-dependent manner. HgCl₂-induced loss of cell viability was not affected by H₂O₂ scavengers catalase and pyruvate, a superoxide scavenger superoxide dismutase, a peroxynitrite scavenger uric acid, and an inhibitor of nitric oxide N^G-nitro-arginine Methyl ester. HgCl₂ did not cause changes in DCF fluorescence, an H₂O₂-sensitive fluorescent dye. The loss of cell viability was significantly prevented by the hydroxyl radical scavengers dimethylthiourea and thiourea, but it was not affected by antioxidants DPPD and Trlox. HgCl₂-induced loss of cell viability was accompanied by a significant reduction in GSH content. The GSH depletion was almost completely prevented by thiols dithiothreitol and GSH, whereas the loss of viability was partially prevented by these agents. Incubation of cells with 0.2 mM buthionine sulfoximine for 24 hr, a selective inhibitor of -glutamylcysteine synthetase, resulted in 56% reduction in GSH content without any change in cell viability. HgCl² resulted in 34% reduction in GSH content, which was accompanied by 59% loss of cell viability. These results suggest that HgCl₂-induced cell death is not associated with generation of H₂O₂ and ROS-induced lipid peroxidation. In addition, these data suggest that the depletion of endogenous GSH itself may not play a critical role in the HgCl₂-induced cytotoxicity in human glioma cells.     

Effect of weight loss on some serum cytokines in human obesity: increase in IL-10 after weight loss

Obesity is a major risk factor for hypertension, coronary artery disease and type 2 diabetes. Weight loss is associated with significant metabolic benefits. Our objective was to examine changes in adipocytokines and interleukin (IL) 10 in obese subjects before and after weight loss. We measured anthropometric parameters, adipocytokine and IL-10 in 78 obese people who had visited obesity clinics at five university hospitals (Ajou, Ulsan, Catholic, Hanyang and Yonsei) in Korea. They restricted their caloric intake to less than their usual intake (by 500 kcal), were administered sibutramine and were given a program of exercise for 12 weeks. After 12 weeks, weight, body mass index, waist circumference, hip circumference, waist-to-hip ratio, total body fat, total cholesterol, triglyceride, tumor necrosis factor alpha (TNF-alpha), IL-6, resistin and leptin had significantly decreased, while adiponectin and IL-10 had significantly increased. A bivariate correlation analysis found that increment in IL-10 and baseline IL-10 levels significantly correlated with decrement in TNF-alpha (P<.01) and baseline adiponectin (r=.52, P<.001), respectively. These results were confirmed in a multiple regression analysis. The results suggest that weight loss after caloric restriction and medical treatment in obesity can improve metabolic risk factors through changes in some cytokines.     

Genetic characterization of the phenylacetyl-coenzyme A oxygenase from the aerobic phenylacetic acid degradation pathway of Escherichia coli

We show here that the paaABCDE genes of the paa cluster responsible for phenylacetate degradation in Escherichia coli W encode a five-component oxygenase that hydroxylates phenylacetyl-coenzyme A (CoA), the first intermediate of the pathway. The primary structure of the subunits of bacterial phenylacetyl-CoA oxygenases revealed that these enzymes constitute the prototype of a new and distinct group of the large bacterial diiron multicomponent oxygenase family.