Separation, amino-terminal sequence and cell-free synthesis of the smallest subunit of sweet potato cytochrome c oxidase

The smallest subunit (V) of sweet potato cytochrome c oxidase was separated into three polypeptides, Va, Vb and Vc with different molecular masses (7.4 kDa, 6.8 kDa and 6.2 kDa respectively) by highly resolving sodium dodecylsulfate polyacrylamide gel electrophoresis. Antibody against subunit V reacted specifically with the polypeptide Vc. When polyadenylated mRNA from sweet potato root tissue was translated in a wheat germ cell-free system, the smallest subunit (Vc) of the polypeptides was synthesized to the same size as the mature form, which suggests that the mature subunit retains the signal for import into mitochondria. Within the N-terminal first 25 amino acids there is a stretch of 16 non-polar residues, periodically linked by basic residues, which might form an amphiphilic helix as the targeting signal.     

Suppression by Exogenous Phospholipid of Cyanide-Insensitive Respiration of Submitochondrial Particles from Sweet Potato Root Tissue

Submitochondrial particles from sweet potato root tissue retainedthe respiratory characteristics of the intact mitochondria withrespect to the sensitivity to cyanide and salicylhydroxamicacid. The activities of total, cyanide-insensitive, and salicylhydroxamate-sensitiverespiration of the submitochondrial particles yielded from adefinite weight of tissue slices incubated under aerobic conditions,particularly in ethylenecontaining air, were higher than thosefrom the same weight of intact tissue. The less phospholipidthe submitochondrial particles contained relative to protein,the higher the activities of cyanide-insensitive and salicylhydroxamate-sensitiverespiration tended to be relative to total respiratory activity.When the submitochondrial particles were incubated with phospholipidliposomes, the activities of cyanide-insensitive and salicylhydroxamate-sensitive,but not cyanide-sensitive, respiration became extremely low.All phospholipids showed this effect. Such incubation of thesubmitochondrial particles with phospholipid liposomes yieldedlighter particles, indicating close association of exogenouslyadded phospholipid with the particles. Phospholipid moleculesseemed to enter the membrane of the particles. We propose thatphospholipid deficiency in the mitochondrial inner membranefacilitates operation of the cyanide-insensitive electron transportpath. (Received March 30, 1984; Accepted June 15, 1984)     

Isolation and Properties of Intact Chromoplasts from Tomato Fruits

Intact chromoplasts were isolated from tomato fruits at differentripening stages by Percoll density gradient centrifugation.The isolated chromoplast fractions were contaminated very littleby other organelles, although the fraction from fully ripenedfruits contained some mitochondria and microbodies. As the transformationof chloroplasts to chromoplasts proceeded, the density of theplastids decreased from 1.096 to 1.075 g-cm^-3 and the decreasewas related to a decrease in chlorophyll and an increase inlycopene in the plastids. (Received December 21, 1983; Accepted April 20, 1984)     

Molecular Cloning and Characterization of a cDNA for the {alpha} Subunit of a G Protein from Rice

We report the isolation of a cDNA for the     

Membranes carrying acid hydrolases in pea seedling roots

Subcellular localization of acid hydrolases in pea seedlingroots was studied by differential and sucrose density gradientcentrifugations. Significant parts of hydrolase activities inthe tissue were recovered in mitochondrial and microsomal fractions.Sedimentable phosphatase was separated into two subtractions:denser and lighter membrane fractions. The distribution of phosphataseactivity after sucrose density gradient centrifugation of thedenser fraction coincided with that of antimycin AinsensitiveNADH-cytochrome c reductase activity. Electron microscopic observationssuggested that the fraction contained only microsomes. RNasein the denser fraction seemed to associate with ribosomes. Phosphataseand RNase were solubilized by sonic treatment in the presenceof high concentrations of salt. On the other hand, a-amylasewas tightly bound to a membrane. The results are discussed withspecial regard to the relationship between the membranes andlysosomes. (Received May 4, 1973; )     

Nucleotide Sequence of cDNA for Concanavalin A from Canavalia gladiata Seeds

We have determined the nucleotide sequence of Con A cDNA forconcanavalin A (Con A) from Canavalia gladiata using a plasmid(pCONAl) that was isolated previously [Eur. J. Bio-chem. (1988)170: 515-520]. This sequence contains a 870-bp open readingframe, a 63-bp 5'-un-translated region and a 99-bp 3'-untranslatedregion. DNA blot analysis suggested that Con A is encoded bya small gene family. In contrast to the case of canavalin, thenucleotide sequence and the genomic organization of Con A geneare highly conserved between C. gladiata and C. ensifor-mis. (Received August 4, 1988; Accepted November 21, 1988)     

IAA-induced opening of excisedMimosa pulvinules

Movement ofMimosa pudica L. pulvinules was investigated by using excised ones which were placed on a moist filter paper. The pulvinules excised in the morning opened at the addition of IAA (10⁻⁷ M to 10⁻⁴M) in the dark. The lag period for the onset of the opening was about 15 min. Na-acetate buffer (pH 4) also induced the opening of pulvinules in the dark, and the buffer-induced opening was inhibited by the uncouplers of oxidative phosphorylation. Na-MES and Na-citrate buffers (pH 4) did not induce the opening. Pulvinules taken from closed leaves in the evening were less responsive to IAA than those taken from open leaves in the morning. The pulvinules taken in the evening slightly opened with incandescent light (4000 lux), but those preincubated with IAA (10⁻⁷M and 10⁻⁶M) opened distinctly upon the illumination.     

Increase in permeability of human endothelial cell monolayer by recombinant human lymphotoxin

The effect of lymphotoxin (LT) on transendothelial permeability was examined using in vitro human endothelial cell (EC) culture system. To assess permeability, we measured the movement of human IgG labeled with horseradish peroxidase (HRP-huIgG) across an EC monolayer cultured on a fibronectin and collagen-coated membrane. LT increases the permeability dose dependently within 16 hours. Similar results were obtained with tumor necrosis factor (TNF)-alpha. The results suggest that increase in vascular permeability by LT and TNF-alpha plays an important role in initiating hemorrhagic necrosis of tumors in vivo.