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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleotide exchange reaction was observed with purified ras oncogene product p21 overproduced in Escherichia coli (Hattori, S. et al. (1985) Mol. Cell Biol. 5, 1449-1455) under various conditions. (NH4)2SO4 increased the rate of dissociation of bound GDP from c-rasH and v-rasH p21. The dissociation kinetics were those of a first order reaction, and there was a linear relationship between the rate constant and the (NH4)2SO4 concentration. At any concentration of (NH4)2SO4, the exchange rate was faster with v-rasH p21 than that with c-rasH p21. EDTA and (NH4)2SO4 synergetically stimulated the dissociation reaction. Nucleotide-free p21 was prepared by gel filtration on Sephadex G-25 in the presence of 5 mM EDTA and 200 mM (NH4)2SO4 at room temperature. The free p21 was quite thermolabile, but the addition of GDP or GTP completely protected p21 from thermal inactivation. The dissociation constants for GDP and GTP were determined with free p21 to be 8.9 and 8.2 nM, respectively, for v-rasH p21, and 1.0 and 2.6 nM for c-rasH p21. In the presence of 200 mM (NH4)2SO4, these dissociation constants increased 3- to 12-fold.
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PMID:Interaction of ras oncogene product p21 with guanine nucleotides. 332 91

Rat pheochromocytoma (PC12) cells differentiate to neuronal cells in response to nerve growth factor. It has been shown that microinjection of oncogenic but not proto-oncogenic p21 protein induces morphological differentiation in PC12 cells (D. Bar-Sagi and J. R. Feramisco, Cell 42:841-848, 1985). In this paper we describe a recombinant human proto-oncogenic Ha-ras protein which can effectively induce neurite extension of PC12 cells when microinjected as a complex with guanosine-5'-O-(3-thiotriphosphate). The protein was found to be less effective when complexed with GTP. On the other hand, an oncogenic ras protein coinjected with guanosine-5'-O-(2-thiodiphosphate) was entirely inactive. These results indicate that the binary p21-GTP complex, but not the p21-GDP complex, is effective in inducing differentiation in PC12 cells, irrespective of the oncogenic or the proto-oncogenic protein.
Mol Cell Biol 1987 Dec
PMID:Induction of neurite formation in PC12 cells by microinjection of proto-oncogenic Ha-ras protein preincubated with guanosine-5'-O-(3-thiotriphosphate). 332 27

An Ala-to-Thr substitution at position 59 activates the transforming properties of the p21ras protein without impairment of GTPase activity, a biochemical alteration associated with other activating mutations. To investigate the basis for the transforming properties of the Thr-59 mutant, we characterized guanine nucleotide release. This reaction exhibited a slow rate and stringent temperature requirements. To further dissect the release reaction, we used monoclonal antibodies directed against different epitopes of the p21 molecule. One monoclonal specifically interfered with nucleotide release, while others which recognized different regions of the molecule blocked nucleotide binding. Mutants with the Thr-59 substitution exhibited a three- to ninefold-higher rate of GDP and GTP release than normal p21 or mutants with other activating lesions. This alteration in the Thr-59 mutant would have the effect of increasing its rate of nucleotide exchange. In an intracellular environment with a high GTP/GDP ratio, this would favor the association of GTP with the Thr-59 mutant. Consistent with knowledge of known G-regulatory proteins, these findings support a model in which the p21-GTP complex is the biologically active form of the p21 protein.
Mol Cell Biol 1986 Dec
PMID:Activation of ras p21 transforming properties associated with an increase in the release rate of bound guanine nucleotide. 354 Jun 8

The three-dimensional structure of trypsin-modified EF-Tu polymers was analyzed to a resolution of 30 A with electron image reconstruction techniques after negative staining. In a 70% saturated ammonium sulfate solution the modified protein forms cylindrical aggregates with a diameter of about 340 A. The repeat distance of the structure along the cylindrical axis is 448 A. The large number of subunits in one repeat hampers the assessment of the helical symmetry. The Fourier analysis and three-dimensional synthesis were therefore carried out with three different selection rules. The three reconstructed density distributions show marked differences. In all of them twofold axes perpendicular to the cylindrical axis are present. The half unit cell content of one of the reconstructions shows a striking similarity with the shape of intact EF-Tu.GDP previously proposed in a similar study. We suggest that in the assemblies investigated here dimers of trypsin-modified EF-Tu.GDP are arranged along a one-start basic helix with 15.4 subunits per turn and a pitch of 64 A. The shape of the monomeric proteolyzed EF-Tu.GDP in this helical arrangement is very similar to that of the intact molecule in cylindrical assemblies studied at this resolution.
J Ultrastruct Mol Struct Res 1986 Mar
PMID:Three-dimensional image reconstruction of helical aggregates of trypsin modified elongation factor EF-Tu from Escherichia coli: comparison with the reconstructed image of intact EF-Tu. 354 59

We characterized the normal (Gly-12) and two mutant (Asp-12 and Val-12) forms of human N-ras proteins produced by Escherichia coli. No significant differences were found between normal and mutant p21 proteins in their affinities for GTP or GDP. Examination of GTPase activities revealed significant differences between the mutant p21s: the Val-12 mutant retained 12% of wild-type GTPase activity, whereas the Asp-12 mutant retained 43%. Both mutant proteins, however, were equally potent in causing morphological transformation and increased cell motility after their microinjection into quiescent NIH 3T3 cells. This lack of correlation between transforming potency and GTPase activity or guanine nucleotide binding suggests that position 12 mutations affect other aspects of p21 function.
Mol Cell Biol 1987 Jan
PMID:Biochemical and biological properties of the human N-ras p21 protein. 355 Apr 23

Isolated cytoplasmic membranes from Micrococcus lysodeikticus were able to incorporate [14C]mannose from GDP-[14C]mannose. Labelled mannose remained in the membrane fraction after its repeated washing and lipid extraction. Sodium dodecyl sulfate gel electrophoresis in 12% acrylamide showed a set of bands with molecular weights ranging from 230 000 to 19 000 which stained for protein and carbohydrate, and incorporated [14C]mannose. Some of these bands reacted with different lectins (concanavalin A, wheat germ agglutinin and ricin). Furthermore, the mannose was incorporated via a glycosylation pathway similar to that followed in eukaryotic system as shown by the preliminary identification of a lipid intermediate transferring the sugar to proteins and by the differential sensitivity to bacitracin and tunicamycin. These complex membrane components were sensitive to digestion with pronase. All the results presented suggest their glycoprotein nature.
Mol Cell Biochem 1986 Feb
PMID:Mannose incorporation and lectin recognition of pronase-sensitive components in Micrococcus lysodeikticus (M. luteus) membranes. 375 4

Trypsin-modified elongation factor (EF-)Tu-GDP from Escherichia coli is known to crystallize in several different unit cells under apparently identical conditions. The crystal polymorphism was investigated and found to be correlated with the source of polyethylene glycol used in the crystallization procedure. The use of highly purified polyethylene glycol promoted the growth of a new crystal form belonging to space group P2(1)2(1)2(1) with cell dimensions of a = 71.9 A, b = 74.7 A, c = 170.9 A and two molecules per asymmetric unit. In extensive crystallization trials, substances that typically contaminate commercial preparations of polyethylene glycol were screened. The final results show that the presence of the divalent anions, HPO4(2-) or SO4(2-), at different concentrations induce the growth of two known crystal forms belonging to space groups C222(1) and P4(3)2(1)2. The relevancy of the findings is discussed.
J Mol Biol 1985 Sep 05
PMID:Induction of elongation factor Tu-GDP crystal polymorphism by polyethylene glycol contaminants. 390 Apr 22

Pure frog retina rod outer segments (ROS) preparations (A280/A500 = 2,1-2,3) catalyze the synthesis of ATP from ADP in the presence of Mg2+. Adenylate kinase (AK) (ATP:AMP phosphotransferase, EC 2.7.4.3) specific activities for ROS preparations are within the range 2-4 mumole per hour for mg protein. The enzymatic activity of investigated preparations is due to intact, but not destroyed ROS. The component which possesses AK is found in water-soluble, but not in membranous ROS fractions and seems to be a part of the predominant ROS plasma protein--GTP-binding complex of transducin. It has been shown, that this component is the T beta subunit of transducin and its enzymatic activity is controlled by other subunits of the transducin complex. The obtained results indicate that GDP kinase (ATP:GDP phosphotransferase, EC 2.7.4.6) activity of transducin depends on the work of both of T beta and T alpha subunits. It has been shown that in the ROS preparations synthesis of the ATP from ADP and GDP phosphorylation are stimulated by a lowering of Ca2+ concentration (less than 10(-5)-10(-7) M). T beta component is suggested to play the role of phosphotransferase which phosphorylates GDP associated with the T alpha subunits and it leads to formation of a complex T alpha X GTP which is an activator of vertebrate retina ROS phosphodiesterase.
Mol Biol (Mosk)
PMID:[Adenylate kinase and GDP-kinase activity of rod outer segments in the frog retina. Possible functional role of the T beta subunit of transducin]. 608 68

Treatment of gp18, a biologically active monomer of the structural protein of the bacteriophage T4 contractile sheath, with 0.6 M-HClO4 leads to the release of GDP, GMP and inorganic phosphate. Each gp18 molecule is shown to carry three atoms of phosphorus. In the isolated protein preparation, gp18 and the nucleoside phosphate are in equimolar relation. It is suggested that in the native sheath-protein subunit, GDP and inorganic phosphate are united as GTP.
J Mol Biol 1984 Nov 05
PMID:On the presence of guanosine phosphate in the tail of bacteriophage T4. 609 55

Amount of guanosine-5'-triphosphate, 3'-diphosphate (pppGpp) and guanosine-5'-diphosphate, 3'-diphosphate (ppGpp) in the cells of b. subtilis increased several times during starvation for lysine or after treatment with serine hydroxamate (analog of serine) or norvaline (analog of leucine), or in the presence of trimethoprim, which induced deficiency of methionine and leucine. In exponentially growing cells the concentration of pppGpp was found to be 10-20 pmol/A600. When serine hydroxamate or trimethoprim were added, concentration of pppGpp increased to 500-800 pmol/A600 and then slowly diminished. Elimination of lysine or addition to the culture medium of norvaline caused slight transitory accumulation of pppGpp (150 pmol/A600). The amount of another nucleotide ppGpp was always 2-3 times lower than one of pppGpp. Accumulation of (p)ppGpp in rel+ cells was accompanied by cessation of stable RNA synthesis. Under conditions described above rel- cells continued RNA synthesis and did not accumulate (p)ppGpp. In the rel+ cells treated with serine hydroxamate synthesis of stable RNA resumed and the amount of (p)ppGpp decreased after addition of serine or tetracycline and chloramphenicol. The half-life period for pppGpp in the presence of chloramphenicol was determined to be 30-40 seconds. Thus, during aminoacyl-tRNA deficiency rel+ cells of B. subtilis accumulate (p)ppGpp, which are believed to participate in negative regulation of RNA synthesis. Slight accumulation of pppGpp without concomitant inhibition of stable RNA synthesis was observed after treatment of growing cells with chloramphenicol.
Mol Biol (Mosk)
PMID:[Guanosine polyphosphate concentration and stable RNA synthesis in Bacillus subtilis following suppression of protein synthesis]. 616 Mar 84


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