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11.
Calmodulin and troponin C: a comparative study of the interaction of mastoparan and troponin I inhibitory peptide [104-115] 总被引:5,自引:0,他引:5
P J Cachia J Van Eyk R H Ingraham W D McCubbin C M Kay R S Hodges 《Biochemistry》1986,25(12):3553-3562
Recent studies using bee and wasp venom peptides have led to the hypothesis that proper complex formation with calmodulin (CaM) requires the presence of a basic amphiphilic helix on the surface of the target protein [Cox, J. A. (1984) Fed. Proc., Fed. Am. Soc. Exp. Biol. 43, 3000]. We have tested this hypothesis by examining CaM and troponin C (TnC) complex formation with two basic peptides, the wasp venom tetradecapeptide mastoparan and the physiologically relevant synthetic troponin I (TnI) inhibitory peptide [104-115], using far-ultraviolet circular dichroism as a secondary structure probe. Complex formation between mastoparan and either CaM or TnC results in an increase in helical content, whereas the helical content of TnI inhibitory peptide does not increase when bound to either protein. Significantly, mastoparan is 78% alpha-helical in a 50% solution of the helix-inducing solvent trifluoroethanol and has a high helix-forming potential according to the Chou-Fasman rules while TnI inhibitory peptide contains none and is not predicted to have any. We interpret these data as indicating that these peptides exhibit substantially different secondary structures upon binding to CaM or TnC. The ability of mastoparan to regulate the acto-subfragment 1-tropomyosin ATPase has also been examined. Mastoparan and TnI inhibitory peptide inhibited 31% and 45% of the activity, respectively. TnC and CaM promote differing degrees of Ca2+-sensitive release of inhibition by both peptides. Sequence comparison suggests that the basic residues present in both peptides are important for binding. However, we conclude that an alpha-helical structure is not a prerequisite for the binding of target proteins to CaM and TnC. 相似文献
12.
Emily L. Germain John W. Littlefield 《In vitro cellular & developmental biology. Plant》1986,22(2):107-112
Summary Stem cells of the embryonal carcinoma cell line called H6 can be induced to differnetiate to endoderm-like cells by retinoic
acid (3×10−6
M). We have detected a diffusible and stable factor which is secreted by H6 endoderm-like cells and stimulates the growth of
H6 stem cells. The stimulation by the endoderm-like cells is considereably greater than that by mouse fibroblasts or H6 stem
cells themselves. No reciprocal stimulation of endoderm-like cells by stem cells occurs. Part but not all of the stimulation
might be due to extracellular matrix proteins or to insulin-like growth factor type 2, each of which also stimulates the growth
of H6 stem cells. Insulin causes no such stimulation.
This work was supported by research rant no. CA-16754 from the National Cancer Institute to J. W. L. E. L. G. was supported
by an American Heart Association Medical Student Research Award.
Editor's Statement This paper presents a good example of cooperativity between undifferentiated teratoma stem cells and differentiated
parietal endoderm-derived countrparts in terms of growth support. It raises the interesting question of the relationship between
factors produced by paprietal and visceral endoderm cells. Gordon H. Sato 相似文献
13.
Conditions have been developed that induce maize (Zea mays L.) protoplasts to re-synthesize cell walls and to initiate cell divisions. Two types of embryogenic maize callus were used as a source of protoplasts: a heterogeneous callus (Type I) derived from immature embryos after three weeks in culture, and a friable, rapidly growing callus (Type II) selected from portions of the Type I callus. Many variables in the growth conditions of the donor tissue (type of medium, transfer schedule, age of callus), protoplast isolation solutions (pH, osmolarity, type and concentration of cell wall hydrolyzing enzymes, addition of polyamines) and conditions (amount of time in enzyme, amount of tissue per volume of enzyme incubation medium, agitation, preplasmolysis of source tissue, type of callus), and purification procedures (filtration and-or flotation), were found to affect both yield and viability of protoplasts (based upon fluorescein-diacetate staining). Our isolation procedure yielded high numbers of viable, uninucleated maize callus protoplasts which were densely cytoplasmic and varied in size from 20 to 50 m in diameter. Protoplasts plated in solid medium formed walls and divided several times. Of several gelling agents tested for protoplast propagation, only agarose resulted in protoplasts capable of sustained divisions leading to the formation of microcalli. Plating efficiency was established over a wide range of protoplast densities (103–107 protoplasts/ml). Highest plating efficiency (25%) was obtained at 1·106 protoplasts/ml). The resulting microcalli grew to be dense clusters of about 0.1–0.5 mm in diameter and then stopped growing. Nurse cultures of maize and carrot (Daucus carota L.), were used to establish that individual protoplasts (not contaminating cells or cell clusters) formed walls and divided. Nurse cultures also increased the efficiency of microcallus formation from protoplasts.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- MS
Murashige and Skoog (1962) salts
- MS 1D
Murashige and Skoog salts with 1 mg/l 2,4-D
- MS 2D
Murashige and Skoog salts with 2 mg/l 2,4-D
- N6
medium of Chu et al. (1975)
- NN67-mod
medium of Nitsch and Nitsch (1967) as modified in the present paper
- FDA
fluorescein diacetate
- LMP
low melting point 相似文献
14.
The effects of nine drugs on the CD spectra of a synthetic calcium binding analog of site III of rabbit skeletal troponin C, can generally be divided into 3 groups: (1) that consisting of haloperidol, benperidol, molindone and promethazine, had no effect on the CD spectrum or calcium sensitivity of the apopeptide; (2) that composed of structurally rigid thioxanthenes, induced CD-detectable structural change in the apopeptide but prevented Ca2+-induced structural change; (3) that consisting of chlorpromazine, trifluoperazine and fluphenazine, induced structural change in the peptide but had no effect on the Ca2+-induced structural change. 相似文献
15.
Sicyos motozintlensis is described from the vicinity of Motozintla de Mendoza, Chiapas. It shows a strong similarity toS. chiriquensis Hammel & D’Arcy from Panama. 相似文献
16.
Monovalent ion stimulated ATPase activity from oat (Avena sativa) roots has been found to be associated with various membrane fractions (cell wall, mitochondrial and microsomal) of oat roots. The ATPase requires Mg2+ (or Mn+2) but is further stimulated by K+ and other monovalent ions. The monovalent ions are ineffective in the absence of the divalent activating cation. The ATPase has been described with respect to monovalent ion specificity, temperature, pH, substrate specificity, and Mg2+ and K+ concentrations. It was further shown that oligomycin inhibits a part of the total ATPase activity and on the basis of the oligomycin sensitivity it appears that at least 2 membrane associated ATPases are being measured. The mitochondrial fraction is most sensitive to oligomycin and the microsomal fraction is least sensitive to oligomycin. The oligomycin insensitive ATPase appears to be stimulated more by K+ than the oligomycin sensitive ATPase. 相似文献
17.
The effect of oral prethcamide (Micoren) (a mixture of two related amides of crotonyl N′ butyric acid) was compared with a placebo preparation in 13 patients with established chronic ventilatory failure. Part I of the study comprised a double-blind single cross-over trial with an initial assessment and two further assessments at the end of each period of one month. Prethcamide was taken in 200-mg. doses four times daily. No subjective or objective changes were noted, and in particular the resting Pco2 showed no change.Part II of the study comprised a double-blind single cross-over trial of the short-term effect of prethcamide compared with placebo in 12 patients in chronic ventilatory failure. Frequent estimations of mixed venous Pco2 were made with a rebreathing technique for four and a half hours after ingestion of prethcamide or placebo preparation.Following prethcamide a fall in Pco2 level to a minimum value at 30 minutes of 93% of control values and persisting for about three hours was noted for the group as a whole. The fall represents a lowering by about 4 mm. Hg of the mixed venous Pco2.It is concluded that, though in patients with chronic ventilatory failure prethcamide may reduce the Pco2 in the short term, there is no subjective benefit or observable objective change following repeated administrations over a period of one month. 相似文献
18.
19.
Effect of trifluoroethanol on protein secondary structure: an NMR and CD study using a synthetic actin peptide. 总被引:11,自引:0,他引:11
The structure of a synthetic peptide comprising the 28 amino-terminal residues of actin has been examined by 1H-NMR and CD spectroscopy. The peptide is largely unstructured and flexible in solution but becomes increasingly structured at higher trifluoroethanol (TFE) concentrations. As judged by CD with the use of two additional peptides (actin 1-20 and actin 18-28), TFE induces formation of up to 48% helical content within residues 1-20, while residues 21-28 exhibit no helical propensity. Similar results were obtained by using NMR-derived distance information in restrained molecular dynamics calculations. The calculated structure of actin 1-28 peptide in 80% TFE is well defined for the first 23 residues with a backbone root mean square deviation of 0.5 A. Two helices are formed from residues 4-13 and 16-20, and a beta-turn is formed from residues 13-16. The N-terminal residues 1-3 exhibit increased flexibility and a helix-like conformation while the C-terminal residues 21-28 show no regular secondary structure. These results are compared with the predicted secondary structure and the structure of the corresponding sequence in the crystal structure of actin [Kabsch et al. (1990) Nature 347, 37-44]. The significance of the TFE-induced peptide structure is discussed. 相似文献
20.