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21.
Expression plasmids encoding native human preporenin and a mutant deleted in its entire prosegment were transfected into Chinese hamster ovary cells. The cells transfected with the expression plasmid of native preporenin secreted exclusively inactive prorenin, while the cells transfected with the mutant secreted the active enzyme. The secreted amount of renin from the latter cells was much lower than that of prorenin from the former ones, although these two enzymes had little difference in specific activity after trypsin activation. These results suggest that the prosegment plays an important role in the secretory process of renin, although the fully active enzyme can be formed in its absence. 相似文献
22.
The regulatory roles of medium pH, a transmembrane pH gradient (delta pH), and an electrical potential (delta phi) on the activation of the N,N'-dicyclohexylcarbodiimide-sensitive Na+/H+-antiporter were studied in the membrane vesicle of Halobacterium halobium in the dark. Neither delta pH nor delta phi independently activated the antiporter but a combination could. The initial rate of Na+ extrusion did not proportionally relate to the size of delta microH+ imposed. The delta microH+-coupled Na+ efflux in the presence of delta phi (-140 mV) increased as external pH decreased, regardless of the size of delta pH, suggesting the existence of one external H+-binding site (apparent pKa 4.6) whose protonation determines primarily the Na+/H+-exchange activity. On the other hand, the dependence of the Na+ efflux on cytoplasmic pH varied with the size of delta pH imposed and the apparent pKa for the cytoplasmic H+ increased with elevating delta pH. The resulting pKa difference across the membrane seems to be the key mechanism for the facilitation of Na+-coupled H+ influx. In other words, delta pH modulates Na+/H+-exchange activity through manipulating the H+ affinity on the cytoplasmic regulatory site. The Na+ extrusion was gated by the threshold delta phi of -100 mV regardless of the size of existing delta pH. delta phi acts on the protonated antiporter and converts it into an active state which becomes delta pH reactive. 相似文献
23.
Irreversible inhibition of v-src tyrosine kinase activity by herbimycin A and its abrogation by sulfhydryl compounds 总被引:21,自引:0,他引:21
Y Uehara H Fukazawa Y Murakami S Mizuno 《Biochemical and biophysical research communications》1989,163(2):803-809
Herbimycin A, an antibiotic which reverses Rous sarcoma virus transformation, inhibited irreversibly the auto- and trans-phosphorylation activities of p60v-src in in vitro immune complex kinase assays. The addition of a sulfhydryl compound such as dithiothreitol, 2-mercaptoethanol, glutathione (reduced form) or cysteine abolished the ability of herbimycin A to inactivate p60v-src kinase as well as the ability to reverse transformed cell morphology, whereas the addition of oxidized glutathione, cystine or methionine showed no effect. The sulfhydryl alkylating reagent N-ethylmaleimide also, although less effectively, inactivated p60v-src kinase activity in vitro. These results suggest the likelihood that sulfhydryl groups of p60v-src are involved in the inactivation of v-src tyrosine kinase activity by herbimycin A. 相似文献
24.
H Watanabe H Miyazaki M Kondoh Y Masuda S Kimura M Yanagisawa T Masaki K Murakami 《Biochemical and biophysical research communications》1989,161(3):1252-1259
Competitive displacement experiments of 125I-endothelin (ET)-1, -2, or -3 binding to chick cardiac membranes were performed with unlabeled ET-1, -2, -3, and sarafotoxin S6b (STX) as competitors. 125I-ET-1 and -2 binding was competitively inhibited by increasing concentrations of these unlabeled peptides in the same order; i.e. ET-2 greater than or equal to ET-1 greater than ET-3 greater than STX. In contrast, the order of potency in displacing 125I-ET-3 binding was ET-3 greater than ET-2 greater than or equal to ET-1 greater than STX. Affinity labeling of the membranes by cross-linking with 125I-ET-1 and -2 via disuccinimidyl tartarate yielded one major specific band with an apparent Mr = 53,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. On the other hand, affinity labeling with 125I-ET-3 showed that two major and one minor bands of Mr = 34,000, 46,000, and 53,000, respectively, were specifically labeled. These results indicate the presence of two distinct types of ET receptors, one of which has higher affinity for ET-1 and -2 than ET-3 and the other is conversely ET-3-preferring. 相似文献
25.
Noriaki Murakami Yoshiyuki Tanaka Kunio Takishima Yuzo Minobe Makoto Matsuoka Sei-Ichiro Kiyota Shin-ichi Hatanaka Katsuhiro Sakano 《Journal of plant research》1990,103(4):419-434
We isolated the small subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO SSu) from a fern,Asplenium cataractarum and determined its 34 N-terminal amino acid sequence. We obtained a cDNA clone that contains the entire coding region of
the SSu from the same fern species, using synthetic oligonucleotide probes derived from the above amino acid sequence. It
contains a 525 bp open reading frame capable of coding for a polypeptide with 174 amino acids, 31 bp 5′-and 206 bp 3′-noncoding
regions. It was also elucidated that the precursor to the SSu contains a transit peptide of 53 amino acid residues and a mature
protein of 121 residues. We compared the deduced amino acid sequence of the fern SSu with those of 11 other vascular plant
species (including gymnosperms, monocots and dicots). As low as 55% homology was observed between those of a fern and seed
plants. Constancy of the amino acid substitution rate in RuBisCO SSu was supported by our relative rate test. Amino acid substitution
rate per year per site for RuBisCO SSu was calculated to be 0.81×10−9 assuming that the separation between pteridophytes and seed plants arose 380 million years ago. 相似文献
26.
27.
Kazuhisa Toyoda Takuya Sugahara Kunio Inouye Koji Yamada Sanetaka Shirahata Hiroki Murakami 《Cytotechnology》1990,3(2):189-197
An immunoglobulin (Ig) production stimulating factor (IPSF) for hybridomas was found in spent medium of the human B lymphoblastoid cell line, HO-323. The IPSF was purified by serial use of DEAE chromatography, ultrafiltration, gel filtration and HPLC-DEAE chromatography. Purified IPSF was estimated to be a 410 k macro molecule by gel filtration, and contained three types of isomers which were separated from each other by native polyacrylamide gel electrophoresis. All of the isomers were, however, assumed to have the same protein components by SDS polyacrylamide gel electrophoresis.The IPSF was effective for human-human and mouse-mouse hybridomas producing IgM, but not for IgG producers in the experimental condition used here. Human-human hybridoma HF10B4, cultured in IPSF-containing medium, produced 20 times more IgM than in IPSF-free medium under serum-free conditions. The IPSF showed very little proliferation stimulating activity on HF10B4 cells. 相似文献
28.
Antizyme, a protein inhibitor of ornithine decarboxylase (ODC), was shown to be induced in mouse kidney by repeated injection of putrescine. Antizyme was also present as a complex with ODC in the kidney of untreated mouse. The amount of the renal ODC-antizyme complex was 3-fold higher in male mice than in female mice. On the contrary, the proportion of ODC present as a complex with antizyme was 24-fold higher in females than in males, and the decay of renal ODC activity after cycloheximide treatment was about 5-fold more rapid in females than in males. Administration of testosterone to female mice, a procedure known to prolong the half-life of renal ODC, increased both ODC activity and the content of ODC-antizyme complex, but decreased the antizyme/ODC ratio in the kidney. These results are consistent with the previous observation in HTC cells that the decay rate of ODC activity in the presence of cycloheximide correlated well with the proportion of ODC present as a complex with antizyme, suggesting the ubiquitous role of antizyme in ODC degradation. 相似文献
29.
Dr. Kenjiro Wake Kiyoyuki Motomatsu Chieko Dan Kenji Kaneda 《Cell and tissue research》1988,253(3):563-571
Summary The three-dimensional structure of endothelial cells in the hepatic sinusoids of the rat was studied by application of light- and electron microscopy on Golgi-impregnated specimens. A number of endothelial cells could thus be individually delineated throughout the hepatic lobules. The cytoplasm, showing heavy silver deposits, consists of two distinct areas, a thick and thin portion. The thick portion, issuing from the region of the perikaryon, branches and tapers toward the cell periphery. The thin portion, occupying the remainder of the cytoplasm, consists largely of highly fenestrated sieve plates. Some intralobular variation can be noted; the thick portion of the endothelial cells is well developed in the periportal zone, while the cells in the centrilobular zone are relatively rich in thin portions. In addition, the area of distribution of an individual endothelial cell is larger in the centrilobular sinusoids than in the periportal zone. Some endothelial cells also possess unique cytoplasmic processes projecting into the intercellular space between hepatocytes and connecting the sinusoidal walls of neighboring sinusoids. These processes may anchor the endothelial cells to the hepatic plates. 相似文献
30.
Ichiro Yamato Hiro Nakamura Hiroshi Murakami Yasuhiro Anraku 《FEMS microbiology letters》1988,56(1):21-27
Abstract The cybB gene on a plasmid encoding cytochrome b 561 in Escherichia coli was disrupted by insertion of Kmrl determinant DNA. The cromosomal cybB gene was replaced by the inactivated cybB gene on the plasmid by homologous recombination using λ phage lysogenization and heat-induction. The replacement was confirmed by Southern and Western blotting analyses. Deficiency on the cybB gene product did not affect the growth properties of the cells, and the oxidase activities of the cells dependent on various substrates were similar to those of the parental strain. Cytochrome b 561 is concluded to be expressed in E. coli , but may not play a major role in cell growth. In the genetic map of E. coli , the cybB gene was determined by conjugational and transductional crosses to be at 31 min between trg and terC . 相似文献