Effects of Preillumination on Dark Nitrogen Fixation and Respiration by Anabaena Cylindrica

In whole filaments of Anabaena cylindrica dark nitrogen-fixingactivity (measured as acetylene reduction) and respiration increasedwith the light intensity of a fixed period of preillumination,saturating at ca. 10,000 lux. With saturating light during preillumination,the amount and duration of dark nitrogen-fixing activity increasedwith length of preillumination, but respiration declined rapidlyin the dark. At dark respiration rates below 250 nmol O₂ uptake mg protein^–1?h^–1(State 1) no significant nitrogen-fixing activity is observed.From 250 to 550 nmol O₂ uptake?mg protein^–1?h^–1(State 2), nitrogen-fixing activity depends on O₂ uptake whileabove 550 nmol O₂ uptake?mg protein^–1?h^–1 (State3), nitrogen-fixing activity no longer increases with furtherincrease in O₂ uptake rate. (Received June 18, 1983; Accepted November 10, 1983)     

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Pharbitis nil, strain Violet which had been exposed to high-intensitylight (18,000 lux at 23?C) for 7 days followed by a low-temperaturetreatment (13–14?C) for 7 days initiated flower buds evenunder continuous light, but plants given these treatments inreverse order failed to bud. Three days of high-intensity lightat 23?C was most effective in promoting the flower-inducingeffect of the subsequent low-temperature period. Six days oflow temperature following the 3-day high-intensity light periodinduced near-maximum flowering response. DCMU (5?10^–6M) given during the high-intensity light period inhibited flowering,but when given during or after the low-temperature period itwas ineffective. DCMU at the same concentration given before,during or after an inductive 16-hr dark period at 26?C did notinhibit flowering. Sucrose, ATP, NADPH and some other reducingagents tested did not nullify the DCMU effect nor substitutefor the effect of high-intensity light. But, the high-intensitylight effect could be substituted, at least partly, by 5-chlorosalicylicacid, 3,4-dichlorobenzoic acid and some other benzoic acid derivatives,which are highly effective in inducing long-day flowering inthe short-day plant, Lemna paucicostata. (Received October 20, 1981; Accepted February 3, 1982)     

Differential effects of oxygen on N2 fixation and C2H2 reduction by Anabaena cylindrica

Both nitrogen fixation and acetylene reduction by intact cellsof Anabaena cylindrica were inhibited by oxygen, but nitrogenfixation was invariably less sensitive than acetylene reduction.The C₂H₂/N₂ ratio ranged from 6 to 8 in the absence of oxygen,and it decreased with increase in partial pressure of oxygento 2 at a pO₂ of 0.3 atm. (Received June 5, 1979; )     

Cloning and characterization of the CYS3 (CYI1) gene of Saccharomyces cerevisiae.

A DNA fragment containing the Saccharomyces cerevisiae CYS3 (CYI1) gene was cloned. The clone had a single open reading frame of 1,182 bp (394 amino acid residues). By comparison of the deduced amino acid sequence with the N-terminal amino acid sequence of cystathionine gamma-lyase, CYS3 (CYI1) was concluded to be the structural gene for this enzyme. In addition, the deduced sequence showed homology with the following enzymes: rat cystathionine gamma-lyase (41%), Escherichia coli cystathionine gamma-synthase (36%), and cystathionine beta-lyase (25%). The N-terminal half of it was homologous (39%) with the N-terminal half of S. cerevisiae O-acetylserine and O-acetylhomoserine sulfhydrylase. The cloned CYS3 (CYI1) gene marginally complemented the E. coli metB mutation (cystathionine gamma-synthase deficiency) and conferred cystathionine gamma-synthase activity as well as cystathionine gamma-lyase activity to E. coli; cystathionine gamma-synthase activity was detected when O-succinylhomoserine but not O-acetylhomoserine was used as substrate. We therefore conclude that S. cerevisiae cystathionine gamma-lyase and E. coli cystathionine gamma-synthase are homologous in both structure and in vitro function and propose that their different in vivo functions are due to the unavailability of O-succinylhomoserine in S. cerevisiae and the scarceness of cystathionine in E. coli.     

Characterization of N omega-phosphoarginine hydrolase from rat liver.

N omega-Phosphoarginine hydrolase from rat liver hydrolyzed N omega-phosphoarginine into arginine and inorganic phosphate, whereas it did not release inorganic phosphate from 19 other phosphorylated compounds containing a N-P bond, an O-P bond or a C-P bond. In addition, it was not able to transfer the phosphoryl moiety from N omega-phosphoarginine to ADP. These results indicated that this enzyme was distinct from both phosphoamidase and arginine kinase. Its properties were as follows: thiol compounds were essential for its activity; it was stimulated by 1.5-2-fold in the presence of 0.001% Lubrol, Tween 20, poly(oxyethylene) 9-lauryl ether and Nonidet P-40, while 0.004% sodium lauryl sulfate inhibited the activity completely; concentrations of sodium molybdate and sodium vanadate necessary for 50% inhibition were 7 microM and 12 microM, respectively; some proteins stimulated the activity, while lysophosphatidic acid, lysophosphatidylinositol, and phosphatidic acid suppressed the activity even in the presence of poly(oxyethylene) 9-lauryl ether.     

Roles of Inorganic Nitrogen in Gametophytic Growth and in Initiation and Development of Sporophytic Shoots of Equisetum arvense

The formation of sporophytic shoots, which is induced by treatmentwith benzylaminopurine of gametophyte tissue of Equisetum arvense,can be divided into initiation and developmental phases. Thenitrogen in MS medium was suitable for two phases as well as gametophytic growth, buta reduction in the concentration of available nitrogen was neededfor the development of shoots. ions alone were effective for gametophytic growth and the initiationof sporophytic shoots, but both and ions was required for the developmental phase. (Received February 18, 1992; Accepted April 14, 1992)     

Nucleotide sequence of the gene coding for four subunits of cytochrome c oxidase from the thermophilic bacterium PS3

The gene coding for four subunits of cytochrome aa3-type oxidase was isolated from a genomic DNA library of the thermophilic bacterium PS3 and sequenced. The N-terminus of each subunit was also sequenced to verify the initiation site of the reading frame. The deduced amino acid sequences contained 615 amino acid residues for subunit I (CO1/caaB product), 333 residues for subunit II (CO2/caaA product), 207 residues for subunit III (CO3/caaC product), and 109 residues for subunit IV (CO4/caaD product) after processing. Re-examination of the sequencing of caa revealed a longer open reading frame for CO1, which contains 14 transmembrane segments instead of 12 [Sone et al. (1988) J. Biochem. 103, 606-610], although the main portions of the sequences constituting cytochrome a (FeA), cytochrome a3 (FeB), and CuB are correct. PS3 CO2 has an additional sequence for cytochrome c after the CuA binding protein portion with 2 transmembrane segments, which is homologous to the mitochondrial counterpart. PS3 CO3 has DCCD-binding glutamyl residues but contains only 5 transmembrane segments, unlike the mitochondrial counterpart, which has 7 segments. The subunits of PS3 cytochrome oxidase (aa3-type) show clear similarity in amino acid sequences with those of cytochrome bo-type oxidase from Escherichia coli as well, in spite of the difference of hemes. PS3 CO3 and CO4 are much more similar to E. coli CO3 and CO4 than to mitochondrial CO3 and CO4, respectively.     

Inhibition of platelet aggregation by S-(1,2-dicarboxyethyl)glutathione, intrinsic tripeptide in liver, heart, and lens

S-(1,2-Dicarboxyethyl)glutathione (DCE-GS) found in animal tissues or baker's yeast showed strong inhibitory effects on blood coagulation and platelet aggregation. The inhibitory effect of blood coagulation was almost the same as those of EDTA, oxalate, and citrate. DCE-GS did not show chelating activity. As for ADP- or thrombin-induced platelet aggregations, DCE-GS exerted a potent effect on the secondary aggregation, while it was less active in the primary aggregation. DCE-GS gave a distinct lag period in the time course of the secondary aggregation induced by collagen and inhibited most strongly the aggregation induced by arachidonic acid compared with those elicited by ADP, thrombin, and collagen. The peptide, however, did not inhibit the platelet aggregation induced by 12-O-tetradecanoylphorbol-13-acetate. Although both DCE-GS and EDTA inhibited the platelet aggregation which was triggered by ADP, their inhibitory manners were entirely different.