Non-cognizable ribonucleotide, 2''AMP, binds to a mutant ribonuclease T1 (Y45W) at a new base-binding site but not at the guanine-recognition site.

Complex of a mutant ribonuclease T₁ (Y4SW) with a non-cognizable ribonucleotide, 2′AMP, has been determined and refined by X-ray diffraction at 1.7 Å resolution. The 2′AMP molecule locates at a new base-binding site which is remote from the guanine-recognition site, where 2′GMP was found to be bound. The nucleotide adopts the anti conformation of the glycosidic bond and C3′-exo sugar pucker. There exists a single hydrogen bond between the adenine base and the enzyme, and, therefore, the site found is apparently a non-specific binding site. The results indicate that the binding of 2′AMP to the guanine-recognition site is weaker than that to the new binding site.     

Function of the N-terminal half of RepA in activation of Rts1 ori.

The RepA protein of the Rts1 plasmid, consisting of 288 amino acids, is a trans-acting protein essential for replication. A mutant repA gene, repA delta C143, carrying a deletion that removed the 143 C-terminal amino acids of RepA, could transform, but at a low frequency, an Escherichia coli polA strain, JG112, when repA delta C143 was cloned into pBR322 with Rts1 ori in the natural configuration. The transformation was less efficient without the dyad DnaA box in the ori region, and no transformation occurred at 42 degrees C, characteristic of Rts1 replication. A fusion of the 3'-terminal half of repA of the P1 plasmid to repA delta C143 yielded a pBR322 chimeric plasmid that contained Rts1 ori through hybrid (Rts1-P1) repA. This plasmid was maintained much more stably in JG112 at 37 degrees C. At 42 degrees C, however, it was quite unstable. The overproduced hybrid RepA protein showed interference with mini-Rts1 replication in trans and also exhibited an autorepressor function, although both activities were decreased. These findings suggest that the N-terminal half of the RepA molecule of Rts1 is involved in the activation of the replication origin.     

Phosphorylation of smg p21B/rap1B p21 by cyclic GMP-dependent protein kinase.

smg p21B/rap1B p21, a member of ras p21-like small GTP-binding protein superfamily, has been shown to be phosphorylated by cyclic AMP-dependent protein kinase (protein kinase A). We show here that this protein was also phosphorylated by cyclic GMP-dependent protein kinase (protein kinase G) in a cell-free system. The same serine residue (Ser179) in the C-terminal region was phosphorylated by both protein kinases G and A. The Km and Vmax values of smg p21B for protein kinase G were 5 x 10(-7) M and 4 x 10(-9) mol/min/mg, and those values for protein kinase A were 1 x 10(-7) M and 3 x 10(-8) mol/min/mg.     

Localization of laminin in nephritic glomeruli as revealed by a quick-freezing and deep-etching method with immunohistochemistry

Summary The three-dimensional localization of laminin in rat glomeruli at the chronic phase of Masugi nephritis was investigated by a quick-freezing and deep-etching method combined with immunohistochemistry. Light-microscopically, laminin was localized in increased mesangial matrix and thickened glomerular basement membrane. The quick-freezing and deep-etching method revealed that the increased mesangial matrix, which was newly formed in axial portions and areas of mesangial interposition, was composed of fine fibrillar networks. They were revealed with the 3,3-diaminobenzidine tetrahydrochloride (DAB) reaction products of peroxidase-labelled secondary antibody following anti-laminin antibody. However, these reaction products were not uniformly distributed in the newly formed matrix. Although the fibrils organizing lamina densa were also immunostained with anti-laminin antibody, the fibrils connected to mesangial cells, podocytes and endothelial cells had smaller amounts of DAB reaction products for laminin. These results indicate that one of the components of fibrils in the mesangial matrix and lamina densa is laminin, which is heterogeneously distributed in the newly formed matrix.     

Immuno-Localization of DEAD Family Proteins in Germ Line Cells of Xenopus Embryos.

In order to investigate whether a vasa -like protein is present in germ line cells of Xenopus , antibodies were produced which react specifically with synthetic oligopeptides of sequences from near the N- or C-termini or with one including the DEAD box of the Drosophila vasa protein.
Only the antibody against the oligopeptide including the DEAD box reacted strongly with germ plasm (GP) or with cytoplasm of germ line cells of Xenopus embryos by immunofluorescence microscopy. By immunoelectron microscopy, the antibody was demonstrated to react with the GP-specific structure, germinal granules, in cleaving embryos, and with their derivatives in the germ line cells of embryos at stages extending from gastrula to feeding tadpole. It also reacted with mitochondria not only in the GP and the germ line cells but also in somatic cells, and with myofibrils in muscle cells. By Western blotting, the antibody was shown to react with several bands of Mr 42–69 ± 10³ in protein samples from Xenopus embryos. In samples from Drosophila ovaries, it reacted with a Mr 71 ± 10³ band which was probably the vasa protein. This indicates the possibility that Xenopus embryos contain several DEAD family proteins. One of these is present on germinal granules, resembling the vasa protein on polar granules of Drosophila .     

L-dopa administration enhances exocytotic dopamine release in vivo in the rat striatum.

Peripheral administration of L-3,4-dihydroxyphenylalanine (L-DOPA) methylester increased extracellular levels of DOPA and dopamine (DA) in the rat striatum monitored by in vivo brain microdialysis. The increase in DA levels persisted after inhibition of DA reuptake by nomifensine. Administration of blockers of voltage-dependent Na+ (tetrodotoxin) or Ca2+ (NKY-722) channels through the dialysis membrane completely eliminated the increase in DA levels. These results demonstrate that the L-DOPA-induced DA release is exocytotic in nature and hence, derived from neurons in the striatum.     

Kinetics of the reconstitution of hemoglobin from semihemoglobins α and β with heme

Kinetics of the reconstitution of hemoglobin from semihemoglobins and with hemin dicyanide have been investigated using three kinds of stopped-flow technique (Soret absorption, fluorescence quenching of tryptophan, and Soret CD). The semihemoglobins and are occupied by heme in the and chains, respectively, the other chain being heme-free. Based on the kinetic results, the following scheme for the reconstitution is proposed; First, hemin dicyanide enters the pocket-like site of the apo chains. Second, in semihemoglobin , the CN-ligand in the fifth coordination position of iron is replaced by the imidazole ring of the proximal His immediately after the heme insertion. In contrast, semihemoglobin changes its conformation after the heme insertion, and this is followed by the ligand replacement. Finally, the partial structure changes induced by the ligand replacement propagate onto the whole molecule and the final conformation is attained. The results indicate that semihemoglobin retains a more rigid and organized structure, and more closely approaches its final structure than does semihemoglobin . Correspondence to: Y. Kawamura-Konishi     

Double-Blind Study of the Chronopharmacotherapy of Depression

To investigate the possibility of chronotherapy with antidepressants for patients with depression, we gave single daily doses of clomipramine 150 mg/day to 30 patients with depression at three different times of day, i.e., morning, noon, or before bedtime, using a double-blind method over a 4-week period. Beneficial effects differed according to the administration time of day, with the most effective result being found for the administration at noon. Time-dependent differences in side effects were observed in tremors and dryness of mouth. An additional 10 patients were administered their medications three times a day by traditional, equally divided doses, and the efficacy was inferior than daily single doses at noon. The study results showed the significance of the administration time of day for the benefits and side effects of antidepressant therapy for depression.