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81.
S-Adenosylmethionine (SAM) synthetase of yeast and hyphal-phase cells of the dimorphic fungusCandida albicans was characterized by kinetic analysis and response to inhibitors. The enzyme from yeast-phase cells has a Km of 0.17 mM for methionine, 0.14 mM for ATP, and is inhibited (in vitro) by dimethyl-sulfoxide, methionine sulfone, and methionine sulfoxide. The hyphal-phase SAM synthetase has a Km of 0.06 mM for methionine, 0.02 mM for ATP, and its activity (in vitro) is enhanced by the substances that inhibit the yeast-phase enzyme. These data strongly suggest that isozymes of SAM synthetase are present inC. albicans and that they are possibly morphology specific. In vivo studies revealed that synthesis of the enzyme is repressed by the addition of methionine to the growth medium and that specific activity of the enzyme increases when intracellular SAM levels are lowered. In addition, it was shown that the increase in specific activity seen during yeast hypha morphogenesis and in yeast cells grown in a methionine-free medium involves de novo protein synthesis. 相似文献
82.
DNA-binding activity associated with the v-myb oncogene product is not sufficient for transformation. 总被引:5,自引:1,他引:4 下载免费PDF全文
The product of the v-myb oncogene of avian myeloblastosis virus is a nuclear protein with an associated DNA-binding activity. We demonstrated that the highly conserved amino-terminal domain of p48v-myb is required for its associated DNA-binding activity. This activity is not required for the nuclear localization of p48v-myb. Furthermore, the associated DNA-binding activity and nuclear localization of p48v-myb together are not sufficient for transformation. 相似文献
83.
Almond plants (Amygdalus communis L. cv. Garrigues) were grown in the field under drip irrigated and non irrigated conditions. Leaf water potential () and leaf conductance (g1) were determined at three different times of the growing season (spring, summer and autumn). The relationships between and g1 in both treatments showed a continuous decrease of g1 as decreased in spring and summer. Data from the autumn presented a threshold value of (approx. –2.7 MPa in dry treatment, and approx. –1.4 MPa in wet treatment) below which leaf conductance remained constant. 相似文献
84.
A E Garcia G Gupta M H Sarma R H Sarma 《Journal of biomolecular structure & dynamics》1988,6(3):525-542
The oligomer d(GCCGCAGC) can adopt two different conformations: i) a duplex with two mismatched A.C base pairs and ii) a hairpin with two C.G base pairs and a single stranded loop. We report molecular mechanics, normal mode analysis, and thermodynamic stability calculations for both structures. We show that the energy-minimized structure and harmonic-dynamics results are in complete agreement with the observed NOE spectrum and imino proton exchange data. We conclude that the high stability of the hairpin structure over the duplex at low salt concentration is due to the higher vibrational entropy contribution to the system free energy by the single stranded loop and to the lack of minor groove phosphate/phosphate electrostatic repulsions that tend to destabilize the duplex. 相似文献
85.
Analysis of the human regulators of complement activation (RCA) gene cluster with yeast artificial chromosomes (YACs). 总被引:6,自引:0,他引:6
D Hourcade A D Garcia T W Post P Taillon-Miller V M Holers L M Wagner N S Bora J P Atkinson 《Genomics》1992,12(2):289-300
The human regulators of complement activation gene cluster (RCA cluster) have been partially characterized with yeast artificial chromosomes (YACs). While the data confirm many points previously elucidated, the finer resolution of YAC mapping has allowed the discovery and/or localization of partial gene duplications, the determination of gene orientations, and the measurement of gaps between known genes. Here nine overlapping YACs that encompass a genomic region of 800 kb, encoding four RCA genes and three gene-like elements, are described. The encoded genes and two of the gene-like elements share the same orientation and are ordered (5' to 3') DAF, CR2, CR1, MCP-like, CR1-like, and MCP. A C4bp-like region lies upstream from DAF and is likely to correspond to one recently observed by F. Pardo-Manuel, J. Rey-Campos, A. Hillarp, B. Dahlback, and S. Rodriguez de Cordoba (1990, Proc. Natl. Acad. Sci. USA 87: 4529-4533). MCP-like, a new genetic element, was discovered and found to be homologous to the 5' portion of the MCP gene. Two large gaps of 85 kb (between CR2 and DAF) and 110 kb (between DAF and the C4bp-like element) could carry additional RCA genes. The arrangement of CR1, MCP-like, CR1-like, and MCP, in that order, strongly suggests that this region was generated by a single duplication of neighboring CR1/CR1-like and MCP/MCP-like forerunners. The RCA YACs will now serve as convenient DNA sources for the subcloning and further characterization of this region. 相似文献
86.
Dr. A. A. Guglielmone A. J. Mangold M. D. Garcia 《Experimental & applied acarology》1991,13(2):129-136
A colony ofAmblyomma parvum was started with engorged females collected from cattle in the Province of Salta (25°01 S, 63°56 W), Argentina. The progeny of those ticks were fed on rabbits and the non-parasitic stages maintained at 27±1°C, 83–86% RH in darkness. The life cycle (prefeeding period not evaluated) had a mean duration of 99.6 days. The mean time (days) for the different phases of the cycle were as follows: feeding period of females, 8.0; pre-oviposition period, 5.7; oviposition period, 17.5; minimum incubation period of the eggs, 31.8; feeding period of larvae, 3.2; premoult period to nymphs, 10.9; feeding period of nymphs, 4.7; premoult period to adults, 17.8. The oviposition pattern was typical of an ixodid tick, including a linear relationship between weights of engorged females and the number of eggs laid (r=0.8659). The males increased 18% in weight after feeding on hosts (P<0.01). The mean recovery rates of larvae, nymphs and females were 28.2%, 95.3% and 90.7%, respectively. The nymphs moulting to females were heavier (6.8±0.69 mg) than those moulting to males (3.2±0.29 mg) (P<0.01). A comparison of biological values ofA. parvum with American and non-AmericanAmblyomma species is presented. 相似文献
87.
The progression of first meiotic prophase and synaptonemal complex (SC) formation in female rats, Rattus norvegicus S.D., is described through the analysis of the different stages of the first meiotic prophase, and confirms the high synchrony of the process in this species. Leptotene is a stage of very short duration and since pairing of the homologues begins very early, only a leptotene-zygotene stage can be distinguished. The progression of pairing during zygotene is asynchronous. The morphology of the SCs is similar to that described in other species. During diplotene and before desintegration of the lateral elements, desynapsis takes place.In some oocytes a double or even multiple nature of lateral elements was seen. Associations between SCs and nucleoli or nucleolar filaments are frequent. The presence of fragmented SCs can be interpreted as a technical artifact. 相似文献
88.
Targets for calcium channel blockers in mammalian skeletal muscle and their respective functions in excitation-contraction coupling 总被引:3,自引:0,他引:3
G Romey L Garcia F Rieger M Lazdunski 《Biochemical and biophysical research communications》1988,156(3):1324-1332
The L-type Ca2+ channel is blocked by 1,4-dihydropyridines (DHP), by phenylalkylamines, by diphenylbutylpiperidines or by benzolactams. We first show with mouse muscle cells in culture that all these L-type Ca2+ channel blockers block contraction. However, voltage-clamp analysis associated to contraction measurements also clearly show that Ca2+ influx through L-type Ca2+ channels is not required for contraction. Therefore, there is a need for a voltage-sensor which would be responsible for the excitation-contraction (E-C) coupling. We are showing here that the voltage-sensor involved in E-C coupling and the L-type Ca2+ channel have a similar pharmacology. Some of the blockers used are more active on the voltage sensor, others on the L-type Ca2+ channel. 相似文献
89.
R Garcia M Cantin A De Léan J Genest J Godin J Gutkowska E L Schiffrin G Thibault 《Biochemical and biophysical research communications》1986,135(3):987-993
The biological activities of ANF (Arg 101-Tyr 126) and of the circulating form, ANF (Ser 99-Tyr 126), were compared in the following assays: precontracted rabbit aortic strip and chick rectum, rat natriuresis, inhibition of aldosterone secretion and receptor affinity in bovine and rat adrenal zona glomerulosa cells, and receptor affinity in rabbit aorta and rat mesenteric artery cells. The results demonstrate that both peptides share the same biological activities. It is concluded that the addition of two amino acids to the N-terminal of ANF (Arg 101-Tyr 126) does not modify its biological characteristics, validating thus previous research employing this peptide. 相似文献
90.
A magnesium-dependent protein kinase activity was copurified with both the molybdate-stabilized 8S form of the chick oviduct progesterone receptor (PR) and its B subunit. In each case, purification was performed by hormonal affinity chromatography followed by ion-exchange chromatography. The Km(app) values of the phosphorylation reaction for [gamma-32P]ATP and calf thymus histones were approximately 1.3 X 10(-5) M and approximately 1.6 X 10(-5) M, respectively, and only phosphorylated serine residues were found in protein substrates, including PR B subunit. Physicochemical parameters of the enzyme [pI approximately 5.3, Stokes radius approximately 7.2 nm, sedimentation coefficient (S20,w) approximately 5.6 S, and Mr approximately 200,000] were compared to those of purified forms of PR (B subunit, pI approximately 5.3, Stokes radius approximately 6.1 nm, and Mr approximately 110,000; 8S form, Stokes radius approximately 7.7 nm and Mr approximately 240,000). The results suggest that most of the protein kinase activity copurified with both oligomeric and monomeric forms of PR belongs to an enzyme distinct from currently known receptor components. Its physiological significance remains unknown. 相似文献