Monoclonal antibodies to mitochondrial coupling factor B

Two monoclonal antibodies (MAb I and IV) have been prepared which showed high and specific reactions towards bovine heart mitochondrial coupling factor B (FB). Both have been identified as sub-type IgG1 of mouse immunoglobulins. MAb I reacts with purified and functionally active FB, alkylated or oxidized forms of FB and even with peptides formed on digestion of FB with trypsin. When used together, MAb I and IV reacted with FB in immunoblots of normal and urea treated samples of mitochondria, submitochondrial particles, ammonia-EDTA extracted particles, and H+-ATPase. Both MAbs inhibited FB-stimulated ATP-dependent reverse electron flow activity when FB was incubated with the antibody either before or after its addition to FB-deficient AE-particles. Reactivity of MAb I towards FB declined upon exposure of FB to guanidine HC1 while reactivity of MAb IV remained unaltered.     

On control of the function of the sodium-potassium pump in malignant cells

This paper introduces a double-layer enzyme-membrane model representing the Na⁺−K⁺ pump in living cells. We present a mathematical solution to the problem of controlling the sodium flux in malignant cells, where an inhibitor exists in the outer layer of the membrane. We give an algorithm for the numerical resolution of this problem of optimal control with illustrations. Finally, we point out the biological importance of this study.     

Structure and genomic organization of a new family of murine retrovirus-related DNA sequences (MuRRS).

A new class of murine retrovirus-related sequences (MuRRS) is described. These 5.7 kb long transposon-like DNA-elements start and end with approximately 600 bp long repeats identical to previously identified solitary LTR-like elements (LTR-IS). There are about 50 - 100 5.7 kb elements and about 500 - 1000 solo LTR-IS elements per mouse haploid genome. Sequence analysis of one cloned MuRRS element revealed several possible open reading frames with partial sequence homologies to retroviral gag, pol and env genes.     

A new syndrome in the group of euhidrotic ectodermal dysplasia

Summary A new form of ectodermal dysplasia was observed in two siblings, offspring of healthy non-consanguineous parents. The main findings in both children are: hypodontia, abnormally shaped teeth, scalp hypotrichosis, pili annulati, follicular hyperkeratosis on the trunk and limbs, intensified delineation and reticular hyperpigmentation of the nape, and hyperopia; one of the siblings also has astigmatism. As both patients have normal nails and are euhidrotic, this is an ectodermal dysplasia of the pilodental subgroup. The cause is probably genetic and autosomal-recessive inheritance is most likely.     

"Allosteric regulation" of calcium-uptake in rat liver mitochondria

During investigations of calcium uptake by rat liver mitochondria, at a buffered free calcium concentration of 2 microM, a considerable acceleration of calcium uptake was occasionally observed. From the following experiments it can be concluded that the acceleration occurred when mitochondria had become anaerobic, and hence deenergized, because they had been stored in the refrigerator for a while. Mitochondria which had become transitorily deenergized by blocking the respiratory chain with KCN, rotenone or antimycin showed an accelerated calcium uptake when the membrane potential necessary for calcium uptake was regenerated. This acceleration of calcium uptake was also seen when a potassium diffusion potential was induced by valinomycin in previously deenergized mitochondria. The velocity of calcium uptake in transitorily deenergized mitochondria increased irrespective of the presence of magnesium in the incubation medium. The activation of the Ca uniporter was reversible, and both processes, activation and deactivation, were time-dependent and developed within a time span of minutes. Oligomycin strongly inhibited the deactivation of the uniporter by ATP, hence the membrane potential is intrinsically effective and does not act via ATP. The altered kinetics of the Ca uniporter were responsible for the acceleration of calcium uptake which was measured at low calcium concentration with previously deenergized mitochondria. The dependence of the rate of calcium uptake on the concentration of calcium in the medium is hyperbolic in transitorily deenergized mitochondria [Km = 6.7 microM; V = 455 nmol/(min X mg protein)] and sigmoidal in normal ones. It is additionally independent of the presence of magnesium ions. We found Hill coefficients of 3.47 and 2.94 in experiments with and without magnesium, respectively. Correspondent kinetics, hyperbolic in deenergized and sigmoidal in normal mitochondria, were obtained when calcium uptake was not driven by the system of respiratory chain, but by the potassium diffusion potential induced by valinomycin. The alteration in the kinetics of the Ca uniporter has consequences in the range of physiological calcium levels, but mainly in pathological states of liver cells. These points are discussed.     

Prevention of aortic lesions and hyperlipidaemia by alfalfa seed extract in cholesterol fed rabbit

Extract of alfalfa seed (ethanolic 50 % v/v) prevents the development of plaque formation and hyperlipidaemia in cholesterol fed rabbits. It inhibits the elevation of serum total cholesterol, triglycerides, phospholipids, LDL-cholesterol and total cholesterol/phospholipid ratio, while HDL-cholesterol/total cholesterol ratio increases, which is associated with a reduced incidence of atherosclerosis. Further reduction in total cholesterol and phospholipid contents of liver and heart muscle are suggestive of a beneficial role of the seed extract. The possible mechanisms of action are discussed.     

Unusual occurrence of EcoP1 and EcoP15 recognition sites and counterselection of type II methylation and restriction sequences in bacteriophage T7 DNA

Selected and counterselected oligodeoxynucleotide sequences were identified in the total sequence of bacteriophage T7 DNA using a statistical criterion derived for a probability model of the Markov chain type. All extremely rare tetra- and pentadeoxynucleotides are (or contain) recognition sequences for the Escherichia coli DNA methylases dam or dcm. Most of the 37 hexadeoxynucleotides absent from T7 DNA are recognition sequences for type II modification/restriction enzymes of E. coli or related species. In contrast to most restriction sites counterselected during evolution, the EcoP1 site GGTCT occurs 126 times in the T7 genome, and phage T7 replication is severely repressed in P1-lysogenic host cells. We demonstrate that the frequency of the EcoP1 site is determined by that of the overlapping recognition sites for T7 primase, an essential phage enzyme. The recognition site of a type III enzyme, EcoP15, is also not counterselected. In T7 DNA all 36 EcoP15 sites are arranged in such a manner that the sequence CAGCAG is confined to the H strand, the complementary sequence CTGCTG to the L strand. This "strand bias" is highly significant and, therefore, very probably selected. A functional relation between this strand bias and the refractive behaviour of phage T7 to EcoP15 restriction is suspected.     

Low-potential cytochrome b as an essential electron-transport component of menaquinone reduction by formate in Vibrio succinogenes

Incorporation of the electron-transport enzymes of Vibrio succinogenes into liposomes was used to investigate the question of whether, in this organism, a cytochrome b is involved in electron transport from formate to fumarate on the formate side of menaquinone. (1) Formate dehydrogenase lacking cytochrome b was prepared by splitting the cytochrome from the formate dehydrogenase complex. The enzyme consisted of two different subunits (M_r 110 000 and 20 000), catalyzed the reduction of 2,3-dimethyl-1,4-naphthoquinone by formate, and could be incorporated into liposomes. (2) The modified enzyme did not restore electron transport from formate to fumarate when incorporated into liposomes together with vitamin K-1 (instead of menaquinone) and fumarate reductase complex. In contrast, restoration was observed in liposomes that contained formate dehydrogenase with cytochrome b (E_m = ?224 mV), in addition to the subunits mentioned above (formate dehydrogenase complex). (3) In the liposomes containing formate dehydrogenase complex and fumarate reductase complex, the response of the cytochrome b of the formate dehydrogenase complex was consistent with its interaction on the formate side of menaquinone in a linear sequence of the components. The low-potential cytochrome b associated with fumarate reductase complex was not reducible by formate under any condition. It is concluded that the low-potential cytochrome b of the formate dehydrogenase complex is an essential component in the electron transport from formate to menaquinone. The low-potential cytochrome b of the fumarate reductase complex could not replace the former cytochrome in restoring electron-transport activity.