General recombination mechanisms in extracts of meiotic cells

RecA-like proteins have been purified from somatic and meiotic cells of mouse and lily. The rec proteins have been designated s-rec and m-rec to indicate their respective tissues of origin. The two proteins differ in molecular weight and in their response to temperature, the latter being consistent with the optimal temperature for physiological function of their tissues of origin. There is a major increase in m-rec protein with the entry of cells into meiosis, the peak of activity being early pachytene. Extracts of the cells and also those of yeast (Saccharomyces cerevisiae) have been prepared that have the capacity to catalyze homologous recombination. These extracts behave similarly to the m-rec proteins upon entry of cells into meiosis. Yeast transferred to sporulation medium displays a 100-fold increase in the recombination activity of the extract at about the time of entry into meiosis. The occurrence of peak levels of m-rec and recombination activity in extracts from cells in early pachytene points strongly to that stage as the time at which the enzymatic phase of recombination occurs.     

Prediction of splice junctions in mRNA sequences.

A general method based on the statistical technique of discriminant analysis is developed to distinguish boundaries of coding and non-coding regions in nucleic acid sequences. In particular, the method is applied to the prediction of splicing sites in messenger RNA precursors. Information used for discrimination includes consensus sequence patterns around splice junctions, free energy of snRNA and mRNA base pairing, and statistical differences between coding and non-coding regions such as periodic appearance of specific bases in coding regions reflecting the non-random usage of degenerate codons. Given the reading frame of an exon (but not the exon/intron boundaries), the method will predict the following exon, namely, the intron to be excised out. When applied to human sequences in the GenBank database, the method correctly identified 80% of true splice junctions.     

Level of translatable messenger RNA coding for argininosuccinate synthetase in the liver of the patients with quantitative-type citrullinemia

Summary The translation activity of mRNA coding for argininosuccinate synthetase in total RNA extracted from the liver of three patients with quantitative-type citrullinemia was determined using a cell-free translation system. In two patients, the hepatic content of the enzyme was about 20% of the control value, whereas translatable mRNA level for the enzyme was similar to or slightly lower than those of control livers. In the third patient, the enzyme content was about 50% of the control value, and mRNA activity for the enzyme was low normal. These results indicate that at least in the first two patients, the decrease in the enzyme protein is due either to increased degradation of the enzyme or to decreased translation in the patient's liver.     

Stereospecific incorporation of hydrogens from NADPH in elongation of very long fatty acyl-CoA by swine cerebral microsomes

The elongation of arachidoyl-CoA by swine cerebral microsomes resulted in the production of behenic acid (22:0) and lignoceric acid (24:0) concomitantly. When 4S-[4-²H₁]NADPH was used for the elongation of arachidoyl-CoA, the incorporation of two deuterium atoms into 22:0 was observed by the technique of mass fragmentography. Furthermore, the incorporation of four deuterium atoms into 24:0 was also detected. On the other hand, when 4R-[4-²H₁]NADPH was used, no deuterium was incorporated into the elongated products.     

CO2 is the first species formed upon CO oxidation by CO dehydrogenase from Pseudomonas carboxydovorans

The active species of CO₂, i.e. CO₂ or HCO ₃ ^- , formed in the CO dehydrogenase reaction was determined using the pure enzyme from the carboxydotrophic bacterium Pseudomonas carboxydovorans. Employing an assay system similar to that used to test for carbonic anhydrase, data were obtained which are quite compatible with those expected if CO₂ is the first species formed. In addition, carbonic anhydrase activity was not detected in P. carboxydovorans.     

Photoreception in pineal organs of larval and adult lampreys,Lampetra japonica

A comparative study of the larval and adult pineal organs, which are sensitive to incident light, was carried out in the river lamprey Lampetra japonica, using intracellular recording from the pineal photoreceptors. The tissue overlying the larval pineal organ is transparent, whereas that over the adult pineal is translucent. The optical density of this oval pineal window in the adult lamprey was 1.2. In order to elucidate the early development of the larval pineal, the ratio r of the diameter (micron) of the pineal to the body-length (cm) was measured. The value of r was 62.5 in a small larva of 2.8 cm, 29.7 in a larger one of 14.3 cm, and 9.3 in an adult of 54 cm body-length. The intracellular response to light of the larval pineal was a hyperpolarization, showing fundamentally the same pattern as that of the adult pineal. It was possible to record a typical response even from the pineal of the smallest larva, 2.8 cm in body length, used in this study. The intensity-amplitude relationship was analysed after Naka-Rushton's hyperbolic equation. The value of sigma of isolated larval pineals was 0.88 log unit higher than that of adults. The value of n was larger in larvae, suggesting a sensitive reaction to changing photic stimulus. The spectral sensitivity was compared. The peak was at 505 nm in the larva, but 525 nm in the adult. A change of visual pigment in the pineal during metamorphosis is suggested.     

Electrophoretic heterogeneity and age-related change of serine proteinase fromAspergillus sojae

Five forms of serine proteinase (EC 3.4.21.14) have been purified fromAspergillus sojae. This paper reports heterogeneity of electrophoretic mobilities, isoelectric points, and kinetic parameters of multiple forms of serine proteinase fromAspergillus sojae, including agerelated changes in thek _cat /K _m of electrophoretic species.