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71.
Solution conformation of endothelin determined by means of 1H-NMR spectroscopy and distance geometry calculations 总被引:4,自引:0,他引:4
H Tamaoki Y Kobayashi S Nishimura T Ohkubo Y Kyogoku K Nakajima S Kumagaye T Kimura S Sakakibara 《Protein engineering》1991,4(5):509-518
The structure of endothelin-1 (ET-1), an endothelial cell-derived peptide with vasoconstricting activity, was determined in an aqueous solution by means of a combination of NMR and distance geometry calculations. The resulting structure is characterized by an alpha-helical conformation in the sequence region, Lys9-Cys15. Furthermore, an extended structure and a turn structure exist in the Cys1-Ser4 and Ser5-Asp8 regions respectively, and no preferred conformation was found for the C-terminal part of the peptide which was not uniquely constrained by the NMR data. These structural elements, the alpha-helical structure in the sequence portion, Cys-X-X-X-Cys, and the extended structure in Cys-X-Cys, are homologous to those found commonly in several neurotoxic peptides. 相似文献
72.
Transmembrane diffusion of hydrophobic antimicrobial agents and cell surface hydrophobicity in Bacteroides fragilis 总被引:1,自引:0,他引:1
The transmembrane diffusion of hydrophobic antimicrobial agents, e.g. lincomycin and clindamycin, was examined in Bacteroides fragilis which is sensitive to these agents. The results showed that these agents penetrate efficiently through the outer membrane. Cell surface hydrophobicity measured by the partition assay between water and p-xylene revealed that the cell surface of B. fragilis is more hydrophobic than that of Salmonella typhimurium or Pseudomonas aeruginosa. Furthermore, treatment with low concentrations of surfactant caused cell lysis. These results suggest that the cell surface hydrophobicity in B. fragilis plays an important role in the efficient transmembrane penetration of hydrophobic compounds. This efficiency explains the susceptibility of B. fragilis to hydrophobic antimicrobial agents. 相似文献
73.
Target size for a fibronectin-cell adhesion system determined by the X-ray inactivation method 总被引:1,自引:0,他引:1
In order to elucidate the mechanism of cell adhesion, the size of the functional site, both in the fibronectin molecule and in the mouse fibroblast cell, responsible for cell adhesion activity, was determined. The size was assumed to be equivalent to the target size, that can be determined from the X-ray inactivation dose. The target size of the cell-binding site in the fibronectin molecule was 32 kdalton. The molecular weight was much larger than that of the tripeptide, which has been reported to be the minimum peptides having a cell-binding activity. This suggests that submolecular regions in fibronectin other than the tripeptide are necessary for cell adhesion. The target size in the cell responsible for the adhesion to the fibronectin-coated surface was 4300 kdalton. The large molecular weight of the target could be explained by assuming that a complex protein system is involved in the cell-adhesion process in the cell. 相似文献
74.
K Kobayashi K Kiuchi A Ishii N Kaneda Y Kurosawa K Fujita T Nagatsu 《FEBS letters》1988,238(2):431-434
Alternative splicing from a single gene produces four kinds of human tyrosine hydroxylase (types 1-4), which have structural diversity only in the N-terminal region. We attempted expression of the type 1-4 enzymes in COS cells and performed kinetic analyses. All had enzymatic activities. The Km values of the four types for L-tyrosine and 6-methyl-5,6,7,8-tetrahydropteridine were similar, although their relative homospecific activities were clearly different. The type 1 enzyme displayed the highest activity. 相似文献
75.
Structure of the horseradish peroxidase isozyme C genes 总被引:13,自引:0,他引:13
K Fujiyama H Takemura S Shibayama K Kobayashi J K Choi A Shinmyo M Takano Y Yamada H Okada 《European journal of biochemistry》1988,173(3):681-687
We have isolated, cloned and characterized three cDNAs and two genomic DNAs corresponding to the mRNAs and genes for the horseradish (Armoracia rusticana) peroxidase isoenzyme C (HPR C). The amino acid sequence of HRP C1, deduced from the nucleotide sequence of one of the cDNA clone, pSK1, contained the same primary sequence as that of the purified enzyme established by Welinder [FEBS Lett. 72, 19-23 (1976)] with additional sequences at the N and C terminal. All three inserts in the cDNA clones, pSK1, pSK2 and pSK3, coded the same size of peptide (308 amino acid residues) if these are processed in the same way, and the amino acid sequence were homologous to each other by 91-94%. Functional amino acids, including His40, His170, Tyr185 and Arg183 and S-S-bond-forming Cys, were conserved in the three isozymes, but a few N-glycosylation sites were not the same. Two HRP C isoenzyme genomic genes, prxC1 and prxC2, were tandem on the chromosomal DNA and each gene consisted of four exons and three introns. The positions in the exons interrupted by introns were the same in two genes. We observed a putative promoter sequence 5' upstream and a poly(A) signal 3' downstream in both genes. The gene product of prxC1 might be processed with a signal sequence of 30 amino acid residues at the N terminus and a peptide consisting of 15 amino acid residues at the C terminus. 相似文献
76.
S Matsubayashi H Tamai N Kobayashi Y Takaichi S Fukata Y Hirota K Kuma T Nakagawa L F Kumagai 《Hormones et métabolisme》1988,20(12):761-764
Angiotensin-converting enzyme (ACE) activity was measured in 10 patients with anorexia nervosa, 6 with hyperthyroid Graves' disease, and 7 with primary hypothyroidism. Patients with anorexia nervosa had a low serum ACE activity (9.8 +/- 2.2 IU/l), as compared to findings in normal subjects (13.4 +/- 3.5 IU/l) (P less than 0.05). Patients with hyperthyroid Graves' disease had high serum ACE activity (23.7 +/- 5.8 IU/l), as compared to levels in normal subjects (P less than 0.01), and patients with primary hypothyroidism tended to have low serum ACE activity (10.1 +/- 1.8 IU/l), compared to the normal subjects (P less than 0.1). Following weight gain (before; 71.3 +/- 10.2% of ideal body weight, after; 88.7 +/- 5.6% of ideal body weight), serum ACE activity in patients with anorexia nervosa reverted to within the normal range (13.8 +/- 3.5 IU/l), and serum T3 concentration was restored to the normal range (before; 0.7 +/- 0.2 ng/ml, after; 1.1 +/- 0.3 ng/ml). In these patients, ACE activity correlated with the per cent of ideal body weight (P less than 0.05). These data suggest that, in underweight subjects with anorexia nervosa, decreased serum ACE activities may relate to emaciation. 相似文献
77.
H Maezawa K Hieda K Kobayashi Y Furusawa T Mori K Suzuki T Ito 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1988,53(2):301-308
In order to examine enhanced killing that might be induced by Auger cascades in the incorporated atoms in cells, bromouracil(BrU)-labelled E. coli cells were irradiated with monoenergetic X-rays at 13.49 and 12.40keV, just above and below the K-absorption edge of bromine. In both cases BrU-labelled cells were more sensitive for killing than were normal cells. However, when the degree of BrU-sensitization was compared between the two energies of X-rays, the enhanced killing at 13.49 keV was only small, 2 +/- 8 per cent based on the D0 value in saline. By the addition of DMSO, which is believed to suppress radical-mediated effects, killing of BrU-labelled cells was enhanced at 13.49 keV by 8 +/- 4 per cent as compared with 12.40 keV, based on D0. These results have been examined in terms of absorbed energy in BrU-labelled cells and in terms of the number of induced Auger events. 相似文献
78.
Temperature effect of the photocyle of sensory rhodopsin (sR) was studied by nanosecond spectroscopy. Though the formation yield of sRM (sR370) was sharply decreased with temperature, those of sRK (sR680) and sRL were insensitive to temperature changes. These results show the existence of the branching process back to sR from sRL. The absorption maxima for sRK and sRL were 595 ± 5 and 555 ± 15 nm, respectively. 相似文献
79.
Scattered light intensity fluctuation in the canine ventricular myocardium: correlation with inotropic drug effect 总被引:2,自引:0,他引:2
D Bose T Kobayashi R A Bouchard L V Hryshko 《Canadian journal of physiology and pharmacology》1988,66(9):1232-1238
Scattered light intensity fluctuation (SLIF) of coherent light by a strip of ventricular muscle during diastole is believed to be due to asynchronous cellular motion within the myocyte as a result of spontaneous release of Ca from the sacoplamic reticulum. Previous studies have shown a correlation between inotropic agents, such as ouabain and elevated extracellular Ca or decreased extracellular Na, and SLIF. The purpose of this study was to see if this correlation could be extended to other inotropic agents. The digitalis genin, ouabagenin, produces inotropy by increasing intracellular free Ca. In toxic concentrations the drug produces abnormal aftercontractions by spontaneous Ca release from the sarcoplasmic reticulum. On the other hand, the Ca channel agonist BAY k 8644 is also positively inotropic, but its effect is associated with a decrease in Ca release from the sarcoplasmic reticulum, manifested by conversion of "rest potentiation" to "rest depression." The effects of these inotropic agents on the power spectra of SLIF were dissimilar. Both frequency and amplitude of SLIF were increased after ouabagenin (1 microM), but these changes were most marked after the onset of toxicity, at which time contractility was decreased, rather than during the positive inotropic response. In contrast, BAY k 8644 (1 microM) decreased SLIF at all levels of inotropic response. The beta-adrenoceptor stimulant drug, dobutamine, and the adenylate cyclase activator, forskolin, produced minimal increase in SLIF at inotropic concentrations but caused a large increase in SLIF only after the onset of toxicity. These results suggest that SLIF is a better indicator of intracellular Ca overload and toxic oscillatory contractions in the presence of an inotrope and not of increased inotropy, per se. 相似文献
80.
Metabolism of galactosylceramide in the twitcher mouse, an animal model of human globoid cell leukodystrophy 总被引:2,自引:0,他引:2
The metabolism of galactosylceramide was investigated in normal and twitcher mice, an animal model for human globoid cell leukodystrophy. The findings were compared with data obtained on human tissues. In vitro studies demonstrated that there were two genetically distinct enzymes that hydrolyze galactosylceramide: galactosylceramidase I and II. The former was deficient in the twitcher, while the latter was intact. beta-Galactosidase preparations purified from normal mouse liver possessed the activity to hydrolyze galactosylceramide when the assay conditions for galactosylceramidase II was used. Therefore, galactosylceramidase II was considered to be identical to GM1 ganglioside beta-galactosidase. In contrast to the human enzyme, the murine beta-galactosidase had a relatively high Km value toward galactosylceramide. The galactosylceramide-loading test demonstrated that the twitcher fibroblasts hydrolyzed the lipid at lower rates than seen in cases of human globoid cell leukodystrophy fibroblasts. These differences in galactosylceramidase II between murine and human tissues suggest that galactosylceramide accumulates in twitcher mice but not in humans with globoid cell leukodystrophy, even though galactosylceramidase I is genetically deficient in both human and this mouse model. 相似文献