A single point mutation confers tetrodotoxin and saxitoxin insensitivity on the sodium channel II

A single point mutation of the rat sodium channel II reduces its sensitivity to tetrodotoxin and saxitoxin by more than three orders of magnitude. The mutation replaces glutamic acid 387 with a glutamine and has only slight effects on the macroscopic current properties, as measured under voltage-clamp in Xenopus oocytes injected with the corresponding cDNA-derived mRNA.     

Isolation of a cDNA encoding the human GM2 activator protein

The GM2 activator protein is a glycolipid-binding protein required for the lysosomal degradation of ganglioside GM2. A human fibroblast cDNA library was screened with mixtures of oligonucleotide probes corresponding to four different areas of the amino acid sequence. A putative clone (821 bp) which gave positive signals to all four probe mixtures was purified and sequenced. The sequence was colinear with the sequence of 160 amino acids of the mature GM2 activator protein. Availability of the cDNA clone should facilitate investigation into function of the GM2 activator protein and also into genetic abnormalities underlying GM2 gangliosidosis AB variant.     

Synthesis of the vasoconstrictor peptide endothelin in kidney cells

The expression plasmid containing human prepro-endothelin cDNA was constructed and introduced into COS-7 cells. Mature endthelin, consisting of 21 amino acid residues, was secreted into the culture medium of the transfected cells and was also synthesized by non-transfected COS-7 cells. Normal kidney cells derived from other species also synthesized and secreted endothelin. Partial characterization of endothelins produced by kidney cells suggested that existence of new types of endothelin. This is the first report of the vasoconstrictor peptide endothelin being synthesized in kidney cells.     

Proteinic prorenin-releasing-stimulator (PRS) in the rat submandibular gland

The release of prorenin as well as renin from rat renal slices was confirmed by a rat prorenin-prosegment ELISA system and an assay system for determining the renin activity. A significant increase of the prorenin release was found by adding rat submandibular gland extract to the slice medium, indicating the existence of a prorenin-releasing stimulator (PRS) in the extract. The pI and molecular mass of PRS were 8.5-8.7 and 28-30 kDa, respectively. The PRS was completely inactivated by boiling or a proteinase treatment.     

Synthesis of human endothelin-1 precursors in Escherichia coli

Endothelin, the most potent vasoconstrictor found in nature, is thought to be important in the regulation of blood pressure and/or local blood distribution. Human placenta cDNA fragment encoding preproendothelin-1 (preproET-1) and its carboxyl terminal mature precursor (C-matured precursor) was expressed in E. coli. These products were characterized by both enzyme immunoassay and Western blot analysis.     

Dual loading of the fluorescent indicator fura-2 and 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) in isolated myocytes

Isolated rat heart myocytes were loaded with both the Ca2+ sensitive fluorescent probe fura-2/AM and the fluorescent pH indicator 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF/AM). Changes in [Ca2+]i and pHi were measured simultaneously using digitized video fluorescence microscopy. In measurement of [Ca2+]i and pHi, the ratios of dual-loaded cells were not different from single-loaded cells. Using this method, [Ca2+]i and pHi in myocytes were 48 +/- 7 nM and 7.17 +/- 0.05. It is concluded that [Ca2+]i and pHi could be measured simultaneously in isolated myocyte using dual-loading of fura-2 and BCECF.     

Cloning and sequence analysis of a cDNA encoding the Rieske iron-sulfur protein of rat mitochondrial cytochrome bc1 complex

We have isolated a cDNA clone for the Rieske iron-sulfur protein of rat cytochrome bc1 complex, by screening a rat liver cDNA expression library using antiserum directed against the corresponding protein of bovine. The amino acid sequence deduced from the nucleotide sequence of the cDNA indicated that the mature polypeptide of the rat protein consists of 196 amino acid residues with a molecular weight of 21,465, and that it is formed as a precursor with an amino-terminal extension. Northern blot analysis indicated that rat liver possibly contains different sizes of mRNAs for the Rieske iron-sulfur protein, and Southern blot analysis demonstrated that rats and mice possess a single gene for this protein.     

Cell type-specific expression of the genes for the protein kinase C family: down regulation of mRNAs for PKC alpha and nPKC epsilon upon in vitro differentiation of a mouse neuroblastoma cell line neuro 2a

By the use of cloned cDNAs for protein kinase C isozymes alpha, beta I, beta II, gamma, and those for novel protein kinase C, epsilon and zeta, the expression of the corresponding mRNA species was examined in various mouse tissues, human lymphoid cell lines, and mouse cell lines of neuronal origin. In adult brain, mRNAs for all the isozymes of PKC family are expressed. However, the expression of these mRNA species in brain is low at birth. A similar pattern of expression was also observed for beta I/beta II mRNAs in spleen. These expression patterns are in clear contrast to that for beta I/beta II mRNAs in thymus where the mRNAs are expressed at birth and the levels of expression decrease with age. Human lymphoid cell lines express large amounts of PKC beta mRNAs in addition to PKC alpha. Further, nPKC epsilon mRNA is expressed in some of these cell lines. On the other hand, all the mouse cell lines of neuronal origin tested express nPKC epsilon and zeta in addition to PKC alpha. In a mouse neuroblast cell line, Neuro 2a, down modulation of mRNAs for both PKC alpha and nPKC epsilon was observed in association with in vitro differentiation.     

Molecular cloning of cDNA for sarcocystatin A and analysis of the expression of the sarcocystatin A gene during development of Sarcophaga peregrina

Sarcocystatin A is a cysteine proteinase inhibitor purified from the hemolymph of Sarcophaga peregrina larvae [Suzuki, T., & Natori, S. (1985) J. Biol. Chem. 260, 5115-5120]. We isolated a cDNA clone for sarcocystatin A and analyzed the structure and expression of the sarcocystatin A gene. Sarcocystatin A consists of 102 amino acid residues. Significant homology was found between amino acid sequences of sarcocystatin A and other mammalian cystatins, and highly conserved sequences among mammalian cystatins were also found in sarcocystatin A. Using cloned cDNA as a probe, we investigated expression of the sarcocystatin A gene during the development of Sarcophaga. Results showed that this gene was transiently activated in the very early embryonic stage and in the pupal stage, suggesting that sarcocystatin A participates in morphogenesis of larval and adult structures of Sarcophaga.     

A toxic substance produced by Nocardia otitidiscaviarum isolated from cutaneous nocardiosis

During our studies on toxic substances from clinically isolated Nocarida, a new isolate identified as Nocardia otitidiscaviarum from cutaneous nocardiosis was found to produce a toxic substance called HS-6 that had strong in vitro as well as in vivo toxicity. The mouse intraperitoneal LD₅₀ value was 1.25 mg/kg and the ED₅₀ value for L1210 cultured cells was 0.3 ng/ml. The structure of HS-6 was determined and found to belong to the 16-membered macrocyclic group with a molecular formula of C₄₃H₆₈O₁₂. HS-6 also showed activity against pathogenic fungi such as Cryptococcus neoformans.