Partial deficiency of hypoxanthine-guanine phosphoribosyltransferase with reduced affinity for PP-ribose-P in four related males with gout

Summary A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5–12% with hypoxanthine and 0.5–3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals.The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10–20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65°C than found with control lysates.     

Eutypa Dieback of Apricot is Prevalent in Switzerland

Ellis, M. B. , Dematiaceous Hyphomycetes. Microbes and Biological Productivity , D. E. HUGHES and A. H. ROSE (Eds.)     

A spectroscopic analysis of the thermally induced folding-unfolding transition of beta-trypsin.

Absorption and fluorescence changes were used to monitor the thermally induced folding-unfolding transition of beta-trypsin. These parameters reflect changes in the microenvironment of different subsets of the four tryptophanyl residues of this protein. The thermal transition was found to be sequential.     

Small-Sized Mutants of SACCHAROMYCES CEREVISIAE

The isolation of mutants of Saccharomyces cerevisiae that divide at approximately half the size of the wild type is described. Three mutants have been isolated in which the small size at bud initiation is due to a mutation in a single nuclear gene.     

Arginine utilization by Mycoplasma fermentans is not regulated by glucose metabolism: A 13C-NMR study

Abstract Electrofusion of protoplasts of two mutant strains of Hansenula polymorpha resulted in high fusion and hybrid yields when the calcium ions present in the conventional fusion medium replaced by zinc ions. The optimal fusion conditions were an alignment field of 0.4 kV cm⁻¹ strength and 2 MHz frequency for 30 s, followed by two consecutive pulses of 12 kV cm⁻¹ strength and 15 μs duration. With 0.05–0.1 mM zinc ions in the fusion medium an average clone number of 10⁴–10⁵ clones per 10⁸ input cells was reached. The presence of about 0.6 mM magnesium ions in the zinc fusion medium was essential.     

Fluorescence Lifetime Imaging of Alterations to Cellular Metabolism by Domain 2 of the Hepatitis C Virus Core Protein

Hepatitis C virus (HCV) co-opts hepatic lipid pathways to facilitate its pathogenesis. The virus alters cellular lipid biosynthesis and trafficking, and causes an accumulation of lipid droplets (LDs) that gives rise to hepatic steatosis. Little is known about how these changes are controlled at the molecular level, and how they are related to the underlying metabolic states of the infected cell. The HCV core protein has previously been shown to independently induce alterations in hepatic lipid homeostasis. Herein, we demonstrate, using coherent anti-Stokes Raman scattering (CARS) microscopy, that expression of domain 2 of the HCV core protein (D2) fused to GFP is sufficient to induce an accumulation of larger lipid droplets (LDs) in the perinuclear region. Additionally, we performed fluorescence lifetime imaging of endogenous reduced nicotinamide adenine dinucleotides [NAD(P)H], a key coenzyme in cellular metabolic processes, to monitor changes in the cofactor’s abundance and conformational state in D2-GFP transfected cells. When expressed in Huh-7 human hepatoma cells, we observed that the D2-GFP induced accumulation of LDs correlated with an increase in total NAD(P)H fluorescence and an increase in the ratio of free to bound NAD(P)H. This is consistent with an approximate 10 fold increase in cellular NAD(P)H levels. Furthermore, the lifetimes of bound and free NAD(P)H were both significantly reduced – indicating viral protein-induced alterations in the cofactors’ binding and microenvironment. Interestingly, the D2-expressing cells showed a more diffuse localization of NAD(P)H fluorescence signal, consistent with an accumulation of the co-factor outside the mitochondria. These observations suggest that HCV causes a shift of metabolic control away from the use of the coenzyme in mitochondrial electron transport and towards glycolysis, lipid biosynthesis, and building of new biomass. Overall, our findings demonstrate that HCV induced alterations in hepatic metabolism is tightly linked to alterations in NAD(P)H functional states.