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1.
Protein kinase C phosphorylates the neurone-specific protein B-50 at a single Ser41 residue, which is also the point for a major proteolytic cleavage in vitro, and probably in vivo, that produces a B-50 phosphorylation-inhibiting N-terminal fragment and a large C-terminal metabolite B-60 (B-50(41-226]. The intact purified protein will bind to calmodulin in the absence of calcium, but the interaction has an absolute requirement for dephospho-B-50. In an attempt to unify two aspects of B-50 biochemistry, we have examined the interaction of B-50 binding to calmodulin and B-50 proteolysis. HPLC- and affinity-purified B-50 bound to calmodulin, but purified B-60 did not. To ensure that this effect was not due to the phosphorylation state of pure, isolated B-60, the metabolite was generated in vitro using a Triton extract of synaptosomal plasma membranes, which contains the as yet uncharacterized B-50 protease. B-60 derived from dephospho-B-50 also failed to bind calmodulin. The results demonstrate a direct connection between B-50 binding to calmodulin and B-50 proteolysis. The position of the proposed calmodulin-binding domain within intact B-50 is discussed in light of the failure of calmodulin to bind B-60. 相似文献
2.
Marina Lotti Michael Noah Marina Stöffler-Meilicke Georg Stöffler 《Molecular & general genetics : MGG》1989,216(2-3):245-253
Summary Ribosomal proteins L4, L5, L20 and L25 have been localized on the surface of the 50S ribosomal subunit of Escherichia coli by immuno-electron microscopy. The two 5S RNA binding proteins L5 and L25 were both located at the central protuberance extending towards its base, at the interface side of the 50S particle. L5 was localized on the side of the central protuberance that faces the L1 protuberance, whereas L25 was localized on the side that faces the L7/L12 stalk. Proteins L4 and L20 were both located at the back of the 50S subunit; L4 was located in the vicinity of proteins L23 and L29, and protein L20 was localized between proteins L17 and L10 and is thus located below the origin of the L7/L12 stalk. 相似文献
3.
Urs Kägi James G. Chafouleas Anthony W. Norman Dr. Claus W. Heizmann 《Cell and tissue research》1988,252(2):359-365
Summary Calcium and intracellular Ca2+-binding proteins are possibly involved in hormone production and spermatogenesis in rat testis. Parvalbumin, calbindin D-28K, S-100 proteins and calmodulin were localized in the Leydig cells, which are sites of testosterone synthesis. Only the appearance of parvalbumin-immunoreactivity is closely correlated to testosterone production during development of the testes. Calbindin D-28K-immunoreactivity persisted in foetal-type Leydig cells and in adult-type Leydig cells at all stages of development. S-100-immunoreactivity was low during all foetal stages, absent between birth and puberty, and increased thereafter. Calmodulin staining is most prominent in the cytoplasm of developing spermatocytes and of maturing spermatids. All four proteins co-exist in the seminiferous tubules. The distinct localization and developmental appearance of these proteins suggests different regulatory roles in Leydig cell function and spermatogenesis. 相似文献
4.
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. 相似文献
5.
N A Sharif N S Pilotte D R Burt 《Biochemical and biophysical research communications》1983,116(2):669-674
Receptors for thyrotropin-releasing hormone (pGlu-His-Pro-NH2, TRH) on thaw-mounted sections of rabbit spinal cord have been identified biochemically and visualized by light microscopic autoradiography. Binding of [3H] [3-Me-His2]TRH to 20 microns sections exhibited high apparent affinity and a pharmacological specificity almost identical to that previously demonstrated for spinal TRH receptors in membranes. In autoradiograms, the highest density of TRH receptors appeared in the substantia gelatinosa of the dorsal gray and around the central canal, with intermediate levels in the ventral gray. 相似文献
6.
Multiple enzyme forms of isocitrate lyase from various sources have been frequently reported. Protease action after cell rupture was sporadically claimed to explain the observed multiple enzyme forms. In this communication studies which are consistent with a protease action in vitro on isocitrate lyase of Pinus pinea germinating seeds are reported. Moreover, changes in DEAE-Sephacel patterns, mainly related to the age of germination, were observed. Differences regarding the heat stability of the detected enzyme forms were also found. The results indicate that isocitrate lyase from P. pinea may be detected in at least three different forms, one of which is heat stable and may be obtained only at the early stages of germination. 相似文献
7.
Inhibition of epidermal metabolism and DNA-binding of benzo[a]pyrene by ellagic acid 总被引:2,自引:0,他引:2
B J Del Tito H Mukhtar D R Bickers 《Biochemical and biophysical research communications》1983,114(1):388-394
Ellagic acid, a common plant phenol, was shown to be a potent inhibitor of epidermal microsomal aryl hydrocarbon hydroxylase (AHH) activity in vitro, and of benzo[a]pyrene (BP)-binding to both calf thymus DNA in vitro and to epidermal DNA in vivo. The in vitro addition of ellagic acid (0.25-2.0 microM) resulted in a dose-dependent inhibition of AHH activity in epidermal microsomes prepared from control or carcinogen-treated animals. The I50 of ellagic acid for epidermal AHH was 1.0 microM making it the most potent inhibitor of epidermal AHH yet identified. In vitro addition of ellagic acid to microsomal suspensions prepared from control or coal tar-treated animals resulted in 90% inhibition of BP-binding to calf thymus DNA. Application of ellagic acid to the skin (0.5-10.0 mumol/10 gm body wt) caused a dose-dependent inhibition of BP-binding to epidermal DNA. Our results suggest that phenolic compounds such as ellagic acid may prove useful in modulating the risk of cutaneous cancer from environmental chemicals. 相似文献
8.
Patricia A. McLenachan Peter J. Lockhart H. Rick Faber Brian C. Mansfield 《Journal of molecular evolution》1996,42(2):273-280
The pregnancy-specific 1-glycoproteins (PSG) form a large family of closely related proteins. Using newly developed methods of sequence analysis, in combination with protein modeling, we provide a framework for investigating the evolution and biological function of genes like the PSG. Evolutionary trees, based on C-terminal sequence, group PSG genes in a manner consistent with their genomic organization. Trees constructed using the N-terminal domain sequences are unreliable as an indicator of phylogeny because of non-neutral processes of sequence change. During duplication of the PSG genes, evolutionary pressures have resulted in a gradient of constrained change across each gene. The N-terminal domains show a nonrandom pattern of amino acid substitutions clustered in the immunoglobulin complementarity-determining region (CDR)-like regions, which appear to be important in the function of the protein. 相似文献
9.
The responses of the field mouse Mus booduga to shifts in schedules of LD cycles were monitored and the results were interpreted with the help of a PRC constructed for the same species. The results reveal that, M. booduga reentrained faster with a lesser number of transients after delay shifts than advance shifts, thus exhibiting “asymmetry effect.” A positive correlation was observed between the number of transients and the number of hours of shift. In most of the shifts, the sign of the transients (negative for delaying transients and positive for advancing transients) coincided with the direction of the shift. Interestingly, 11 and 12 h of advance shifting resulted in delaying transients. An 11-h advance shift can also be interpreted as a 13-h delay. Reentrainment through delaying transients is faster as compared to reentrainment through advancing transients. Thus, this animal might have taken a “shorter route,” as proved by the fact that an 11-h advance shift has evoked delaying transients. But a 13-h advance shift evoked only advancing transients. This prompts us to speculate that there may be a “phase jump” in M. booduga. Further, irrespective of whether L or D has been doubled in a 12-h shift, both evoked only delaying transients. 相似文献
10.
Christa Schleper Richard Röder Tatjana Singer Wolfram Zillig 《Molecular & general genetics : MGG》1994,243(1):91-96
Three phenotypically stable mutants of the extremely thermophilic archaeon Sulfolobus solfataricus have been isolated by screening for -galactosidase negative colonies on plates with X-Gal (5-bromo-4-chloro-3-indolyl-(3-d-galactopyranoside). From one of these mutants an insertion element, designated ISC1217, was isolated and characterized. Sequence analysis of ISC1217 and of the regions adjacent to the insertion site in the -galactosidase gene revealed features typical of a transposable element: ISC1217 contained terminal inverted repeats and was flanked by a direct repeat of 6 bp. The 1147 by sequence contained an open reading frame encoding a putative protein of 354 amino acid residues and, overlapping this, two smaller open reading frames on the opposite strand. There were approximately 8 copies of the insertion element in the S. solfataricus genome. ISC1217 did not cross-hybridize with DNA of other Sulfolobus species. All three independently isolated -galactosidase mutants of S. solfataricus arose by transposition of ISC1217 or a related element. 相似文献