O dealkylation and aliphatic and aromatic hydroxylation of 3-methoxy-17 beta-estradiol by Aspergillus alliaceus

Aspergillus alliaceus UI 315 was examined for its ability to metabolize 3-methoxy-17 beta-estradiol. Preparative-scale incubations with this substrate afforded good yields of 6 beta-hydroxy-17 beta-estradiol, 4-hydroxy-17 beta-estradiol, and 4,6 beta-dihydroxy-17 beta-estradiol, which were identified by high-pressure liquid chromatography, 1H and 13C nuclear magnetic resonance, and high-resolution mass spectrometry.     

Mutations in the signal sequence of prepro-alpha-factor inhibit both translocation into the endoplasmic reticulum and processing by signal peptidase in yeast cells.

The effects of five single-amino-acid substitution mutations within the signal sequence of yeast prepro-alpha-factor were tested in yeast cells. After short pulse-labelings, virtually all of the alpha-factor precursor proteins from a wild-type gene were glycosylated and processed by signal peptidase. In contrast, the signal sequence mutations resulted in the accumulation of mostly unglycosylated prepro-alpha-factor after a short labeling interval, indicating a defect in translocation of the protein into the endoplasmic reticulum. Confirming this interpretation, unglycosylated mutant prepro-alpha-factor in cell extracts was sensitive to proteinase K and therefore in a cytosolic location. The signal sequence mutations reduced the rate of translocation into the endoplasmic reticulum by as much as 25-fold or more. In at least one case, mutant prepro-alpha-factor molecules were translocated almost entirely posttranslationally. Four of the five mutations also reduced the rate of proteolytic processing by signal peptidase in vivo, even though the signal peptide alterations are not located near the cleavage site. This study demonstrates that a single-amino-acid substitution mutation within a eucaryotic signal peptide can affect both translocation and proteolytic processing in vivo and may indicate that the recognition sequences for translocation and processing overlap within the signal peptide.     

Tyrosination-detyrosination of tubulin and microtubules during the development of chick erythrocytes

The protein composition of nuclear matrices containing different amount of DNA was examined. It was found that, in matrices containing 2% to 80% of total DNA, the quantity of DNA-bound proteins remains relatively constant varying from 10% to 15% of total nuclear proteins. Electrophoretic patterns do not differ substantially, but autoradiograms with in vitro ¹²⁵I labelled proteins show quantitative variations in the actin content. Application of radioimmunoassay (RIA) enabled to determine the exact content of actin in GAT nuclei and nuclear matrices – 5 g/ml in nuclei, of which 50% are bound to DNA and 3001o being a component of the protein part of the nuclear matrix. These results are supported by electron microscopic data, where immunogold technique was performed on thin sections and spread material. The applied methods suggest that part of the nuclear actin is tightly bound (resistant to 2 M NaCI) to DNA and represents a component of the internal nuclear matrix.     

Renin release responses to in vitro prostaglandin challenge in the summer-active ground squirrel, Spermophilus lateralis

1. Using a renal cortical slice preparation from the summer-active ground squirrel, Spermophilus lateralis, resting renin release (RR) and tissue cyclic AMP content (TcAMPC) levels were found to be significantly higher and lower, respectively, than those previously reported for its hibernating counterpart. 2. At a 10(-5) M dose, PGE2 but not PGE1, PGF2-alpha or PGA1, significantly stimulated RR in the summer-active ground squirrel (SAGS). 3. Addition of agents which normally increase TcAMPC significantly potentiated the effect of PGE1, while preventing that of PGE2, on RR and TcAMPC. 4. Opposite TcAMPC changes may mediate the in vitro RR responses to PGE1 and PGE2 administration in the SAGS.     

Spectral features of amines of 2-phenylbenzazoles upon interaction with DNA

Absorption and fluorescent spectra of various synthetic aminophenyl derivatives of benzoxazole, benzothiazole and benzimidazole have been studied to estimate the efficiency of their binding with DNA. The significance of different functional groups of the fluorochromes for their interaction with DNA was determined, and main demands are formulated to the compounds to be used as potential fluorescent probes for DNA studies.     

Cyclic analogs of des-Arg9-[Leu8]bradykinin

Four cyclic derivatives of des-Arg9[Leu8]bradykinin have been obtained by classical methods of peptide chemistry. They are cyclo-(-X-Arg-Pro-Pro-Gly-Phe-Gly-Pro-Leu-), where X=Lys or none, and cyclo-(Y-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu-), where Y= Lys or Orn. Peptide bonds have been formed by the pentafluorophenylester method, and cyclization has been carried out in a diluted dioxane solution with 40% yield. Subsequent cleavage of protecting groups was made by treatment with hydrogen fluoride. The products obtained were purified by droplet counter-current chromatography. These substances liberate histamine from the rat mast cells comparably to bradykinin and fail to produce myotripic and vascular effects.