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31.
Evidence that the G1-S and G2-M transitions are controlled by different cdc2 proteins in higher eukaryotes. 总被引:71,自引:0,他引:71
Xenopus eggs contain two distinct cdc2 homologs of 34 and 32 kd. We show that the 32 kd cdc2 protein, like the 34 kd protein, is a kinase. However, unlike the 34 kd homolog, the 32 kd cdc2 kinase activity does not decrease dramatically at the end of mitosis. The 32 kd protein does not associate with mitotic cyclins B1 and B2 but does associate with cyclin A and a novel doublet of proteins of 54 kd that may regulate its activity. We also show that depletion of the 32 kd cdc2 homolog from a Xenopus extract blocks DNA replication, but does not inhibit entry into mitosis. By contrast, depletion of the 34 kd cdc2 homolog or absence of mitotic cyclins from an extract does not inhibit replication, but does block entry into mitosis. Our results indicate that in higher eukaryotes, DNA replication (G1-S) and mitosis (G2-M) may be controlled by distinctly different cdc2 proteins. 相似文献
32.
Rong-Xiang Fang Zhen Pang Dong-Ming Gao Ke-Qiang Mang Nam-Hai Chua 《Plant molecular biology》1991,17(6):1255-1257
33.
M. Yang Fang Ming J. Hubble A. D. Lockett R. R. Rathbone J. A. Howell 《Biotechnology Techniques》1992,6(5):409-412
A simple thermal monitoring technique has been successfully applied to an adsorption system using a novel ion exchanger with
a large internal void volume (voidage) which can be operated at high superficial velocity (SV). Temperature changes resulting
from heats of adsorption could be followed effectively using semi-conductor thermistor devices inserted into the resin through
the column wall. Results show that, despite the high feed rates adopted, the thermal signals generated can be consistently
related to the position of the breakthrough front within the bed. 相似文献
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Studies of bovine hypothalamic cyclic nucleotide phosphodiesterase (PDE) indicate the presence of several peaks of PDE activity,
distinguishable by DEAE-cellulose column chromatography, displaying different substrate specificities, kinetic behavior, and
regulatory properties. Evidence is presented that chromatographically separated forms of PDE activity are subject to control
by Ca2+-calmodulin, cyclic nucleotides, limited proteolysis, reagents affecting sulfhydryl groups, and neurohormone “C”—one of several
new cardioactive compounds isolated from hypothalamic magnocellular nuclei of animals—in a complex substrate-specific and
concentration-dependent manner. Of particular interest is the finding that each of the forms of cGMP PDE, being Ca2+/calmodulin-dependent, possesses sensitivity to activation by cAMP, especially under conditions favoring the oxidation of
thiol groups of PDE, resulting in a loss in responsiveness of the enzyme to the activation by calmodulin. This effect appears
to be relatively stable but readily reversible by sulfhydryl reducing reagents, which restore both the cGMP PDE sensitivity
to competitive inhibition by cAMP and the responsiveness of the enzyme to activation by calmodulin. A reinterpretation of
the regulatory properties of multiple forms of PDE is proposed.
Special Issue dedicated to Dr. Eugene Kreps. 相似文献
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O. N. Danilevskaya E. V. Kurenova B. A. Leibovitch A. Ya. Shevelev I. A. Bass R. B. Khesin 《Molecular & general genetics : MGG》1984,197(2):342-344
Summary We have isolated restriction fragments from a shotgun collection of Drosophila DNA which function as autonomously replicating sequences (ARS) in Saccharomyces cerevisiae and hybridize with telomeric regions of the 2L, 2R, 4, and X chromosomes. In an independently obtained set of D. melanogaster clones five fragments hybridize in situ with telomeres and a number of internal sites. Two of them also contain ARSs. A Drosophila mobile P-element also possesses ARS activity in yeast. 相似文献
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