Primary structure of Saccharomyces cerevisiae NADPH-cytochrome P450 reductase deduced from nucleotide sequence of its cloned gene

We isolated cDNA (pgCYR, about 2.1 kb) and genomic DNA (pgGYR, about 4 kb) clones coding for NADPH-cytochrome P450 reductase by immunoscreening of yeast Saccharomyces cerevisiae cDNA and genomic DNA libraries in phage lambda gt11. The clones were sequenced and found to encode a protein of 691 amino acid residues with a calculated molecular weight of 76,737 daltons. The amino-terminal sequence (excluding the initial methionine residue) deduced therefrom was in agreement with the protein sequence of the yeast reductase. In addition, the deduced sequence included the partial amino acid sequence determined with the papain-solubilized reductase. The total amino acid sequence of the yeast reductase showed 33-34% similarity with those of the rat, rabbit, pig, and trout reductases. In spite of low similarity in the total amino acid sequences, the possible functional domains related to binding of FAD, FMN, and NADPH were well conserved among all five species compared.     

Identification of both calpains I and II in nucleated chicken erythrocytes

Chicken erythrocytes were found to contain two species of calpains which differ in elution profile from DEAE-cellulose and in Ca2+ requirement. After partial purification, one of them was half-maximally activated by 10 microM Ca2+ and the other by 180 microM Ca2+. The low- and high-Ca2+-requiring proteases cross-reacted only with the respective monospecific antibodies for mammalian calpain I and calpain II, respectively. Approximately 5 times more calpain I than calpain II is present in chicken erythrocytes. By immunoelectrophoretic blot analysis, both calpains I and II from chicken erythrocytes were proved to be heterodimers composed of 76 and 28 kDa, and 80 and 28 kDa subunits, respectively. Our present finding that the heavy subunit of calpain I is smaller than that of calpain II is noteworthy, since the opposite is known to be true of various mammalian calpains. An immunological study has revealed that the calpain I newly found in chicken erythrocytes is not derived from calpain II. Thus, the co-existence of calpains I and II in one animal species also holds in chickens, contrary to the previously advocated notion that chickens have only one type of calpain.     

Membrane potential in liposomes measured by the transmembrane distribution of 86Rb+, tetraphenylphosphonium or triphenylmethylphosphonium: effect of cholesterol in the lipid bilayer

Valinomycin-induced potassium diffusion potential (delta psi, inside negative) in the liposomes made of phosphatidylcholine and various amounts of cholesterol was measured by uptake of 86Rb+, tetraphenylphosphonium (TPP+) or triphenylmethylphosphonium (TPMP+). In any liposome, the values of membrane potential obtained by 86Rb+ uptake (delta psi Rb) agreed well with those calculated from the imposed potassium concentration gradient using the Nernst equation, and were not affected by the presence of cholesterol. However, both delta psi TPP and delta psi TPMP showed smaller values than delta psi Rb when the cholesterol content in liposomes increased. delta psi TPMP at a stationary state was much smaller than delta psi TPP. The orientational order parameter of the lipids' bilayer with various cholesterol content was estimated from fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. The results indicated that the permeation of TPP+ or TPMP+ into liposomes containing a large amount of cholesterol is strongly restricted by the high ordering of phosphatidylcholine acyl chains.     

A kinetic study of the inhibition of yeast AMP deaminase by polyphosphate

Inorganic pyrophosphate and polyphosphates have acted as potent inhibitors of purified AMP deaminase (EC 3.5.4.6) from yeast: the activity fell to a definite limit with the increase in the concentration of the inhibitor. The effect of polyphosphate was largely on the maximal velocity of the enzyme with some decrease in affinity. The cooperative effect of AMP, analyzed in terms of a Hill coefficient, remained at 2 in the absence and presence of polyphosphate. Binding of polyphosphate to the enzyme showed no cooperativity. The inhibition of AMP deaminase by polyphosphate can be qualitatively and quantitatively accounted for by the partial mixed-type inhibition mechanism. Both the Ki value for the inhibitor and the breakdown rate of the enzyme-substrate-inhibitor complex are dependent on the chain length of polyphosphate, suggesting that the breakdown rate of the enzyme-substrate-inhibitor complex is regulated by binding of polyphosphate to a specific inhibitory site.     

Existence of antizyme and ornithine decarboxylase-antizyme complex in RK13 kidney cells

It has been reported that 'antizyme', a protein inhibitor of ornithine decarboxylase (ODC) induced by its product, is not found in rat or mouse kidney. We determined whether antizyme was present in rabbit kidney cells (RK13) in culture. Antizyme could be induced in these cells by putrescine treatment, a substantial portion being in the particulate fraction in contrast with hepatic antizyme. Furthermore, ODC-antizyme complex was present even in untreated cells. Pretreatment of cells with putrescine increased the relative amount of ODC-antizyme complex and accelerated decay of ODC. These results support the ubiquitous existence of antizyme and its role in ODC degradation.     

Fluctuations in follicular structures of rat thyroid glands during 24 hours: fine structural and morphometric studies

The thyroid follicles of adult male Wistar rats were examined at six evenly spaced times over 24 hr with a morphometric technique. Follicular structures were subjected to distinct variations during 24 hr, with respect to volume and numerical densities of follicles in the thyroid gland, and diameters, volumes, cell numbers, and luminal surface areas of individual follicles. Variations in follicular structures were divided into two phases: a large follicular phase at 1200, 1600, and 2000 hr and a small follicular phase at the other times. Although volume densities of follicles in the gland varied with a small amplitude, diameters, volumes, and cell numbers of individual follicles exhibited distinct fluctuations during 24 hr. Numerical densities of follicles in the gland changed distinctly during the small follicular phase as well. Degenerating follicular cells appeared in the follicular lumen especially at 1600 hr. No mitotic follicular cells were found throughout the experiment. Furthermore, one to three follicular cells of two adjacent follicles were often in contact with each other at 0400, 0800, and 1200 hr, and these follicles were lined by the common basement membranes. These results suggest that the variations in follicular structures during the small follicular phase occur in the form of follicle separation and fusion. Moreover, the morphological and morphometric variations in follicles reflect those in subcellular structures of follicular cells previously reported by us.     

Bimodal variations in subcellular structures of rat thyroid follicular cells during 24 hours: fine structural and morphometric studies

To clarify 24-hr variations in rat thyroid follicular cells under physiological conditions, their subcellular structures were examined at six evenly spaced times during 24 hr by using a morphometric technique. The volume, surface, and numerical densities of subcellular structures varied distinctly over each 24-hr period, with a bimodal pattern. The cellular and nuclear volumes varied also bimodally over 24 hr. A decrease in the surface density of the apical plasmalemma at 1200 and 0000 hr coincided with an increase in volume density of cytoplasmic granules representing colloid droplets and dense bodies. Most granules (colloid droplets) appearing at these times were reduced in electron density. At other times, especially at 1600 and 0400 hr, morphometric parameters of rough endoplasmic reticulum (rER), Golgi complex, and subapical vesicles were prominently increased, although values for rER did not peak at 1600 hr. At these times, the volume densities of cytoplasmic granules, most of which were heterogeneous and of homogeneous electron density, were decreased. These findings coincided with immediate and subsequent reactions of follicular cells after injection of thyroid-stimulating hormone (TSH). From the evidence, it seems likely that variations in follicular cells over a 24-hr period reflect variations in blood TSH concentration. The total membrane areas of membrane components in follicular cells were calculated from the morphometric measurements. These areas fluctuated unimodally during 24 hr over a 65% range. This suggests that the membranes in follicular cells are subjected to cyclic degradation and regeneration during each 24-hr period.     

Scavenger receptor for malondialdehyde-modified high density lipoprotein on rat sinusoidal liver cells

We report here the presence of a membrane-associated receptor which mediates endocytic uptake of malondialdehyde-modified high density lipoprotein (MDA-HDL) on sinusoidal liver cells. Binding of [125I]MDA-HDL to the cells was followed by internalization and degradation in lysosomes. The binding and lysosomal degradation of [125I]MDA-HDL were effectively inhibited by unlabeled MDA-HDL and acetyl-HDL. However, formaldehyde-treated serum albumin or low density lipoprotein modified either by acetylation or malondialdehyde, ligands known to undergo receptor-mediated endocytosis by sinusoidal liver cells, did not affect the binding of [125I]MDA-HDL to the cells. These results indicate that a receptor for MDA-HDL is described as a distinct member among the scavenger receptors for chemically modified proteins.     

Cholera toxin, a potent inducer of epidermal hyperplasia but with no tumor promoting activity in mouse skin carcinogenesis

Intracutaneous injection of cholera toxin into mice induced epidermal hyperplasia to a greater extent than 12-O-tetradecanoylphorbol-13-acetate. It also induced adenylate cyclase and though weakly, ornithine decarboxylase of the epidermis. Cholera toxin, however, showed no tumor promoting activity in mouse skin carcinogenesis. In the single stage promotion, cholera toxin (50 ng) was injected once a week for 10 weeks into the skin of SENCAR mice initiated with 25 micrograms 7,12-dimethylbenz[a]anthracene, but no tumors developed. In the two-stage promotion test, cholera toxin (10-100 ng) was injected for one or two weeks into the initiated skin and then mezerein (4 micrograms) was applied twice a week for 18 weeks, but the toxin did not increase incidence or numbers of papillomas.     

Solid-phase syntheses of oligodeoxyribonucleoside methylphosphonates

Oligodeoxyribonucleoside methylphosphonates of defined sequence of the type d-Np(NP)nN, where n is 6-13, are readily prepared on insoluble polystyrene supports by use of protected 5'-(dimethoxytrityl)deoxyribonucleoside 3'-(methylphosphonic imidazolides) as synthetic intermediates. The imidazolides are prepared in situ by reaction of protected 5'-(dimethoxytrityl)deoxyribonucleoside with methylphosphonic bis(imidazolide) and can be stores in the reaction solution for up to 2 weeks at 4 degrees C with no loss in activity. The condensation reaction is accelerated by the presence of tetrazole, which appears to act as an acid catalyst. The half-life for dimer formation on the polystyrene support is 5 min, and the reaction is 95% complete after 60 min. Although similar kinetics are observed when controlled pore glass is used as the support, the extent of the reaction does not go beyond 78%, even after prolonged incubation. In order to simplify purification and sequence analysis of the oligomer, the 5'-terminal nucleoside unit is linked via a phosphodiester bond. This linkage may be introduced by either an o-chlorophenyl phosphotriester method or a cyanoethyl phosphoramidite method. The latter procedure simplifies the deprotection step, since the cyanoethyl group is readily cleaved by ethylenediamine, which also removes the base protecting groups and cleaves the oligomer from the support. The singly charged oligomers are easily purified by affinity chromatography on DEAE-cellulose. The chain lengths of the oligomers were confirmed after 5'-end labeling with polynucleotide kinase by partial hydrolysis of the methylphosphonate linkages with 1 M aqueous piperidine followed by polyacrylamide gel electrophoresis of the hydrolysate.(ABSTRACT TRUNCATED AT 250 WORDS)