Coordination distortion induced water adsorption in hydrophobic flexible metal-organic frameworks

Herein, we synthesized four isostructural flexible interdigitated hydrophobic metal-organic frameworks that differ only in their central metal ion. The water-adsorption properties are dependent on the metal species, which was revealed to be caused by coordination distortion around the metal ions.

[Serum transferrin receptor level as an index of the response to erythropoietin therapy for anemia in pre-dialysis patients with chronic renal failure]

In order to reveal whether serum transferrin receptor (sTfR) can serve as an index in erythropoiesis during recombinant human erythropoietin (rHuEpo) therapy for anemia in pre-dialysis patients with chronic renal failure, we analyzed hematopoietic parameters and sTfR levels in 26 patients who were newly administered rHuEpo. sTfR was determined as sTfR transferrin complex (TRC) using the enzyme linked immunosolvent assay (ELISA) and the latex agglutination nephelometric immunoassay (LA). The therapeutic effect of rHuEpo was expressed as the change in the Ht from the start of treatment to 8 weeks later. (delta Ht). Ht, RBC and Hb levels were significantly increased at 4 and 8 weeks after initiating rHuEpo treatment. Furthermore, sTfR levels were significantly increased at 2 and 4 weeks after the start of rHuEpo treatment. Absolute changes in the sTfR level (sTfR before - sTfR after) and rates of change (absolute change/sTfR before x 100) at, 2, 4 weeks after the start of rHuEpo treatment showed a significant positive correlation with delta Ht. These results indicate that sTfR is a useful marker as an index of therapeutic effect of rHuEpo for anemia in pre-dialysis patients with chronic renal failure.

cDNA cloning of nuclear localization signal binding protein NBP60, a rat homologue of lamin B receptor, and identification of binding sites of human lamin B receptor for nuclear localization signals and chromatin

We previously purified and characterized a nuclear localization signal (NLS) binding protein, NBP60, in rat liver nuclear envelopes. In this study, we cloned and sequenced the cDNA of rat NBP60, and predicted an amino acid sequence comprising 620 amino acids. The sequence revealed that NBP60 is a rat homologue of lamin B receptor (LBR), and is 79 and 63% identical in amino acids to human and chicken LBR, respectively. Using three fusion proteins containing different parts of the amino-terminal domain of human LBR, it was shown that the stretch comprising amino acids 1 to 89, which contains a Ser-Arg rich region (RS region), binds to nucleoplasmin and that the binding was inhibited by a common NLS-peptide. These results suggested that the amino-terminal domain of LBR contains an NLS-binding site. Furthermore, it was shown that the stretch comprising amino acids 1 to 53, which does not contain the RS region or the predicted DNA-binding site, binds to Xenopus laevis sperm chromatin.

Soluble transferrin receptor-transferrin complex in serum: measurement by latex agglutination nephelometric immunoassay

The transmembrane protein, transferrin receptor (TfR), exists in serum as a soluble form that lacks cytoplasmic and transmembrane domains (residues 1-100). The level of soluble TfR in serum is a sensitive indicator of total erythropoiesis and iron deficiency. This study revealed that the major part of soluble TfR was saturated by transferrin (Tf) in serum, forming a stable complex which was more immunoreactive than intact TfR. Thus, we proposed that serum soluble TfR should be measured as the TfR-Tf complex (TRC), using prepared TRC for assay standardization. We developed a new assay for TRC, employing antibody-coated latex agglutination nephelometry (LA). Rapid and reproducible measurements were achieved using an automated analyzer. The values obtained by this LA assay were closely correlated with those obtained by conventional enzyme immunoassay (r = 0.967). The mean level of TRC in 179 adult healthy subjects was 1.62 mg/l. Patients with iron-deficient anemia showed significantly higher TRC levels than the healthy subjects.

Properties of rat liver signal peptidase reconstituted into liposomes

EDTA/KCl- or pyrophosphate-treated rough microsomes of rat liver clearly showed the co-translational cleavage of pre-human placental lactogen and translocation of the product into membrane vesicles. The signal peptidase fraction was isolated by chromatography on Sephacryl S-300 of deoxycholate-treated membranes and reconstituted into liposomes by dialysis or by the Biobeads SM-2 method. Assay of the signal peptidase activity was performed with pre-human placental lactogen synthesized by the reticulocyte lysate system programmed with human placental lactogen mRNA. The signal peptidase reconstituted into liposomes showed stable activity over the temperature range of 0 to 45 degrees C; in contrast, the detergent-solubilized signal peptidase of dog pancreatic membranes was completely inactivated at the unusually low temperature of 37 degrees C. It was shown that this inactivation was due to the presence of detergent. Signal peptidase from rat liver was insensitive to a variety of protease inhibitors, like the enzyme from dog pancreas, but differed from the latter in being inhibited by chymostatin and TPCK.

Interaction of secretory protein precursors with phospholipids in liposomes

The precursors of secretory proteins were synthesized in a reticulocyte lysate system programmed with rat serum albumin or human placental lactogen mRNA and their interaction with phospholipids in liposomes was studied. The precursor proteins could bind to acidic phospholipids that have an exposed phosphate such as dicetyl phosphate and phosphatidic acid or a phosphate that is covered by a small moiety such as phosphatidylglycerol. The binding of precursor proteins was dependent on the mol% of acidic phospholipids in lecithin-liposomes, increased with elevation of temperature in the range of 0 to 45 degrees C, and was not inhibited by the addition of a large excess of mature proteins. Mature proteins or proalbumin showed no significant binding to the liposomes containing acidic phospholipids. About 15% of the acid-precipitable radioactivity bound to the liposomes was resistant to protease digestion. This radioactivity was shown to correspond to methionine-containing peptides with molecular weights of 2,500 to 3,500. These results indicate that the post-translational insertion of a small part of the precursor proteins into the membrane did occur with the present model system, but the post-translational transfer of precursor proteins across the membrane did not.