FEBS Letters
0014-5793
Cơ quản chủ quản: WILEY , Wiley-Blackwell
Lĩnh vực:
Molecular BiologyBiochemistryBiophysicsGeneticsCell BiologyStructural Biology
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Mitochondrial autonomy: Synthesis of DNA from RNA templates in isolated mammalian mitochondria
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Identification of a Baeyer–Villiger monooxygenase sequence motif Baeyer–Villiger monooxygenases (BVMOs) form a distinct class of flavoproteins that catalyze the insertion of an oxygen atom in a C–C bond using dioxygen and NAD(P)H. Using newly characterized BVMO sequences, we have uncovered a BVMO‐identifying sequence motif: FXGXXXHXXXW(P/D). Studies with site‐directed mutants of 4‐hydroxyacetophenone monooxygenase from Pseudomonas fluorescens ACB suggest that this fingerprint sequence is critically involved in catalysis. Further sequence analysis showed that the BVMOs belong to a novel superfamily that comprises three known classes of FAD‐dependent monooxygenases: the so‐called flavin‐containing monooxygenases (FMOs), the N ‐hydroxylating monooxygenases (NMOs), and the BVMOs. Interestingly, FMOs contain an almost identical sequence motif when compared to the BVMO sequences: FXGXXXHXXX(Y/F). Using these novel amino acid sequence fingerprints, BVMOs and FMOs can be readily identified in the protein sequence databank.
Tập 518 - Trang 43-47 - 2002
Glucose stimulates the biosynthesis of rat I and II insulin to an equal extent in isolated pancreatic islets The effects of glucose on insulin biosynthesis were studied by measuring the incorporation of radiolabelled amino acids into proinsulin/insulin in isolated rat islets. The islets were pulse labelled for 15 min with [3 H]leucine (present in rat insulin I and II) or [35 S]methionine (unique to rat insulin II) and then incubated for a 165 min post‐label (chase) period during which the majority of labelled proinsulin was converted to insulin but under conditions whereby > 95% of radiolabelled proinsulin or insulin was retained in the islets. The newly synthesized, labelled, insulin was analyzed by high performance liquid chromatography. Rat I and II insulin biosynthesis was stimulated by 16.7 mM glucose to the same extent.
Tập 215 - Trang 179-182 - 1987
Inhibition of <i>N</i>‐acetylneuraminate lyase by <i>N</i>‐acetyl‐4‐oxo‐D‐neuraminic acid We show that the 4‐oxo analogue of N ‐acetyl‐D‐neuraminic acid strongly inhibits N ‐acetylneuraminate lyase (NeuAc aldolase, EC 4.1.3.3) from Clostridum perfringens (K
i = 0.025 mM) and Escherichia coli (K
i = 0.15 mM). In each case the inhibition was competitive.
Tập 232 - Trang 145-147 - 1988
Evidence for solvent‐induced conformational changes of the soluble <i>Dunaliella</i> chloroplast coupling factor 1 (CF<sub>1</sub>) The ATPase activity of the chloroplast coupling factor 1 (CF1 ) isolated from the green alga Dunaliella is completely latent. A brief heat treatment irreversibly induces a Ca2+ ‐dependent activity. The Ca2+ dependent ATPase activity can be reversibly inhibited by ethanol, which changes the divalent cation dependency from Ca2+ to Mg2+ . Both the Ca2+ ‐dependent and Mg2+ ‐dependent ATPase activities of heat‐treated Dunaliella CF1 are inhibited by monospecific antisera directed against Chlamydomonas reinhardi CF1 . However, when assayed under identical conditions, the Ca2+ ‐dependent ATPase activity is significantly more sensitive to inhibition by the antisera than is the Mg2+ ‐dependent activity. These data are interpreted as indicating that soluble Dunaliella CF1 can exist in a variety of conformations, at least one of which catalyzes a Ca2+ ‐dependent ATPase and two or more of which catalyze an Mg2+ ‐dependent ATPase.
Tập 171 - Trang 262-266 - 1984
Lipopolysaccharide treatment in vivo induces tissue expression of GTP cyclohydrolase I mRNA A significant induction of GTP cyclohydrolase I (GTPCH) mRNA was observed in lung, heart and kidney of rats treated with lipopolysaccharide (LPS; 10 mg/kg i.v.). GTPCH mRNA levels in liver were high even in untreated rats, and remained elevated after LPS treatment. Parallel induction of nitric oxide synthase (NOS) mRNA was observed in these tissues of LPS‐treated rats. Our results demonstrate induction of GTPCH mRNA after LPS treatment in vivo and provide molecular evidence for the increased GTPCH activity which may up‐regulate NOS activity in vivo.
Tập 368 - Trang 336-338 - 1995
Identification of functional type 1 ryanodine receptors in mouse dendritic cells Ca2+ signaling plays an important role in the function of dendritic cells (DC), the specialized antigen‐presenting cells of the immune system. Here we describe functional ryanodine receptor (RyR) Ca2+ release channels in murine, bone marrow‐derived DC. RT‐PCR analysis identified selective expression of the type 1 RyR, with higher levels detected in immature rather than mature DC. The RyR activators caffeine, FK506, ryanodine and 4‐chloro‐m ‐cresol mobilized Ca2+ in DC, and responses to 4‐chloro‐m ‐cresol were inhibited by dantrolene. Furthermore, activation of RyRs both inhibited subsequent inositol trisphosphate‐mediated Ca2+ release and provoked store‐operated Ca2+ entry, suggesting a functional interaction between these intracellular Ca2+ channels. Thus, the RyR1 channel may play an intrinsic role in Ca2+ signaling in DC.
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Improved antiviral activity of the aryloxymethoxyalaninyl phosphoramidate (APA) prodrug of abacavir (ABC) is due to the formation of markedly increased carbovir 5<sup>′</sup>‐triphosphate metabolite levels The anti‐human immunodeficiency virus (HIV) activity of abacavir (ABC; 1‐(1S ,4R )‐4‐[2‐amino‐6‐(cyclopropylamino)‐9H‐purin‐9‐yl]‐2‐cyclopentene‐1‐methanol) could be markedly enhanced by administering the aryloxymethoxyalaninyl phosphoramidate prodrug derivative of ABC (pro‐ABC‐MP) to virus‐infected cell cultures. Metabolic studies with radiolabeled ABC and pro‐ABC‐MP in human T‐lymphocyte and primary macrophage cell cultures revealed a significantly increased delivery of the activated (phosphorylated) metabolite of ABC (ABC‐MP) by pro‐ABC‐MP, and the concomittant appearance of markedly higher intracellular levels of carbovir 5′ ‐triphosphate (CBV‐TP), which represents the eventual antivirally active metabolite of ABC. The intracellular amounts of ABC‐MP and appearance of CBV‐TP closely correlated with the extracellular pro‐ABC‐MP concentrations that were administered to the cell cultures within a concentration range between 0.5 and 100 μM. The highest amounts of CBV‐TP were observed within 6–24 h after drug administration. The improved delivery of ABC‐MP and metabolic conversion to CBV‐TP explain the markedly enhanced antiviral activity of the prodrug of ABC, and warrant further exploration of this prodrug technology on ABC and related compounds to further enhance and optimize their antiviral efficacy.
Tập 573 - Trang 38-44 - 2004