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

The carboxypeptidase previously described that releases tyrosine from tubulinyl-tyrosine was obtained from rat brain preparation free of tubulin-tyrosine ligase. The enzyme was purified 24-fold. Its activity was increased by 2 mM MgCl2 or 30 mM KCl. Mercaptoethanol (50 mM), colchicine (0.2 mM) and tyrosine (0.2 mM) showed practically no effect on the release of tyrosine whereas iodoacetate (2 mM), deoxycholate (0.5%), CuCl2 (0.1 mM), ZnCl2 (0.1 mM) and NaCl or KCl (240 mM) had a strong inhibitory effect. The optimal pH of this enzyme was 6.3--7. A preparation containing tubulin-tyrosine ligase free of carboxypeptidase was also obtained. This preparation catalyzed the release of tyrosine from tyrosinated tubulin in the presence of ADP, Mg2+, K+ and Pi and the incorporation of tyrosine into tubulin. For the releasing activity the optimal concentration of MgCl2 was 3--20 mM and of KCl was 10--30 mM. For ADP the maximal act;vity was at 0.3 mM or higher. An important difference between the activities of the carboxypeptidase and the ligase was that the former was active on denatured tubulin whereas the latter was not.
Mol Cell Biochem 1978 Feb 24
PMID:Release of [14C]tyrosine from tubulinyl-[14C]tyrosine by brain extract. Separation of a carboxypeptidase from tubulin-tyrosine ligase. 2 79

The distribution of disulfide-groups was investigated in the tunica propria of human seminifersou tubules by means of a thiosulfation/Alcian Blue + 0.8 Mol MgCl2-staining reaction. Controls had shown the absence of significant amounts of sulfhydryl- or sulfate-groups in the lamina propria, which groups would also be demonstrated by the method employed. The lamina propria of human seminiferous tubules is rich in disulfide groups. The staining reaction decreases in the region of the tubulus rectus, is only faint in the connective tissue which underlies the epithelium of the rete testis, and is absent in the lamina propria of efferent ducts. It is suggested that microfibrils and type IV collagen (both rich in cystine) are the materials responsible for the histochemical reaction described. The occurrence of multiple layers of basal lamina material (type IV collagen) and bundles of microfibrils is shown in comparative electron microscopic studies.
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PMID:Histochemical demonstration of disulfide-groups in the lamina propria of human seminiferous tubules. 7 13

Bound and solubilized ATPase from Escherichia coli show similar kinetic properties. The saturation curves for MgATP are hyperbolic with both preparations. The straight lines in the Line-weaver-Burk plot indicate that MgATP is the true substrate, that one molecule MgATP is bound per enzyme molecule, and that there is no cooperativity. Presence of EDTA leads to sigmoidal saturation curves. This effect could be reversed by adding MgCl2 stoichiometrically to EDTA. Different results in other publications, especially in that of CARREIRA and MUNOZ1 can be explained as being primarily the consequence of complexing agent contaminations in the assay.
Mol Cell Biochem 1977 Apr 12
PMID:Kinetic properties of soluble adenosine triphosphatase of Escherichia coli. 14 5

It was shown that chromatin isolated from the liver of adult rats is an effective cell-free system for studying DNA synthesis without using exogenous enzymes or DNA-template. Both replication synthesis initiated in vivo and unscheduled synthesis activated several fold after gamma-irradiation of isolated chromatin proceed in chromatin preparations. Unscheduled synthesis consists of template-dependent and template-independent synthesis. Template-dependent synthesis proceeds with a maximum rate in the presence of all four deoxynucleoside triphosphates (dNTP). Template-independent synthesis proceeds with an appearable maximum rate in the presence of one dNTP whose incorporation is inhibited by the addition of the rest dNTP. All three DNA synthesis in chromatin are ATP-dependent. Replication synthesis but not the unscheduled one is inhibited by actinomycin D and N-ethylmaleinimide. Repair inhibitor--0.01 M caffeine--suppresses the initiation of unscheduled synthesis, but does not influence its elongation. The incubation conditions of chromatin for unscheduled synthesis are optimalized as for temperature, pH, time of incubation, qualitative ionic composition of the medium, concentration of chromatin, ATP, dNTP, MgCl2, NaCl. Michaelis constants for TTP are equal to 1 mM for template-independent synthesis and 3 mM for template-dependent synthesis. At optimal conditions DNA of chromatin is lengthened by 8 X 10--3% as the result of template-dependent synthesis and by 1 X 10--3% as the result of template-independent. The transition from nuclei to chromatin as well as the purification of chromatin from nuclear membranes enhance the rate of unscheduled synthesis. On the other hand, addition of nucleoplasm or cell extract to the chromatin does not considerably influence the synthesis. So it is suggested that the enzymes of initiation and elongation of unscheduled DNA synthesis are concentrated in the chromatin. The plausible role of unscheduled synthesis in excision and postreplication repair of eukaryotic DNA is discussed.
Mol Biol (Mosk)
PMID:[Endogenous DNA synthesis in isolated chromatin]. 20 78

The present work outlines various kinetic parameters of the interaction between bGH (bovine growth hormone) and a receptor located on the membranes of rabbit liver. A dissociation procedure, which strips the hormone off its receptor has been worked out, by varying MgCl2 concentrations and times of contact; exposure to 4 M MgCl2 for 15--30 min was found optimal for dissociation, without denaturing the receptor, as shown by the possibility of rebinding the hormone to the desaturated membranes. This method has been applied to titrate growth hormone receptors in rabbit liver, during pregnancy and lactation. The first half of pregnancy is characterized by a gradual increase of receptor levels and low saturation by endogenous hormone; conversely at parturition, there occurs a striking increase in receptors, which, however, may be demonstrated only after desaturation. During the lactational period, the receptors reamin in part saturated. The results suggest that growth hormone levels increase at parturition and during lactation in the rabbit and hence may play an important role during lactation. The factors which modulate receptor levels at the same period remain unknown.
Mol Cell Endocrinol 1979 Jan
PMID:Titration of total binding sites for growth hormone in rabbit liver. Quantitative modifications of these sites during pregnancy. 22 Dec 84

Polyuridilic acid of average molecular weight 18 000 binds to the 30S subunits with stoichiometry 1 : 1 but two kinds of 30S.poly(U) complexes with different stability are formed. The main reason for such heterogeneity was found to be due to the presence or absence of ribosomal protein Sl in 30S subunits. In its presence the association constant of 30S.poly(U) complex is equal 2.7.10(8) M-1, and in the opposite case it is much less 1.5.10(6) M-1. In the same conditions (20 mM MgCl2, 200 mM HN4Cl, 0 degrees) the association constant of binary complex Sl.poly(U) is equal 5.10(7) M-1.
Mol Biol (Mosk)
PMID:[Quantitative studies of interaction of polyuridylic acid with 30S subunits of ribosomes of Escherichia coli]. 37 17

We have studied the effects of Co2+ and Mn2+ ions on the low-field nuclear magnetic resonance (NMR) spectra of pure class 1 transfer ribonucleic acid (tRNA) species. With 1.2 mM tRNA in the presence of 15 mM MgCl2 discrete paramagnetic effects were observed for Co2+ at concentrations in the range 0.02--0.1 mM and for Mn2+ in the range 0.002--0.01 mM, indicating fast exchange of these cations with tRNA. Both of these cations paramagnetically relax the s4U8--A14 resonance as well as other resonances from proximal base pairs. The Co2+ site appears to be the same site on G15 which was observed crystallographically [Jack, A., Ladner, J. E., Rhodes, D., Brown, R. S., & Klug, A. (1977) J. Mol. Biol. 111, 315-328]; the initially occupied tight Mn2+ site is the cation site involving the phosphate of U8. There are three base pairs within 10 A of both sites, namely, G15--C48, A14--s4U8, and C13--G22; this has led to the assignment of the G15--C48 and C13--G22 resonances in the NMR spectrum [Jack, A., Ladner, J. E., Rhodes, D., Brown, R. S., & Klug, A. (1977) J. Mol. Biol. 111, 315--328; Holbrook, S. R., Sussman, J. L., Warrant, R. W., Church, G. M., & Kim, Sung-Hou (1977) Nucleic Acids Res. 4, 2811--2820; Quigley, G. J., Teeter, M. M., & Rich, A. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 64--68].
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PMID:Paramagnetic ion effects on the nuclear magnetic resonance spectrum of transfer ribonucleic acid: assignment of the 15--48 tertiary resonance. 38 41

Disulfide-groups are demonstrated in the basement membranes of glomerular capillaries, proximal convoluted tubules, and collecting ducts by means of a thiosulfathion/Alcian Blue +0.8 Mol MgCl2-staining sequence. It is suggested that the reaction shows type IV collagen of basal lamina material, which is characterized by a relatively high cystine content (8 half-cystine residues/1000).
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PMID:Histochemical demonstration of type IV collagen in the renal glomerulus. 64 Aug 66

Chromatin which was hydrodynamically sheared in a low ionic strength buffer lacking divalent cations (mu = 0.005) contains a heterogeneous set of DNP particles but no molecules of free DNA. The main finding is that a transference of sheared chromatin to 1-2 mM MgCl2 or to 0.1-0.2M NaCl results in the appearance of completely free DNA molecules. A salt-induced rearrangementof DNA-bound histones, but not a partial loss of them is responsible for the observed phenomenon. Formation of free DNA molecules is accompanied by aggregation of the majority of remaining DNP particles. Percentage of free DNA molecules in the chromatin which was sheared to an average DNA length of approx. 400 base pairs is increased from zero in the initial DNP sample to 8-9% in 1 mM MgCl2 and further to 30-31% of the total DNA in 0.30 M NaCl, 2 mM MgCl2. Free DNA molecules in the sheared chromatin are observed not only upon isopycnic banding of formaldehyde-fixed DNP in CsCl gradients but also in non-ionic Metrizamide gradients with either fixed or unfixed DNP samples. Process of free DNA formation is a reversible one; its direction and the equilibrium state depend in particular on the ionic conditions of the medium. Percentage of free DNA molecules in the sheared chromatin at a given ionic strength of solution is strongly decreased upon an increase of the average length of DNA in the DNP particles. Several lines of evidence suggest that free DNA molecules are formed in the sheared chromatin as a result of cooperative rearrangements of histones in salt-induced DNP aggregates. A dynamical model of chromosomal fiber is proposed on the basis of the present and earlier experimental data [1]. According to the model histones are arranged on DNA in clusters separated by stretches of free DNA. A salt-induced migration of histones along or between DNP fibers can result in unification of different clusters, thereby generating longer stretches of free DNA, the total amount of free DNA being approximately constant. Possible in vivo significance of such a dynamical structure is discussed.
Mol Biol (Mosk)
PMID:[Structure of chromosomal deoxyribonucleoproteins. VII. Free dna in preparation of fragmented chromatin]. 98 44

An endogenous Ca2+, Mg2+-dependent factor of enzymic nature (apparently an endonuclease) digests a part of chromatin in the rat liver nuclei producing DNA fragments of an uniform size. After 60 min of incubation at 15 degrees C and pH 7.50 in the presence of 5 mM MgCl2 and 2 mM CaCl2 87-93% of the total chromatin becomes soluble. The insoluble chromatin however contains 70-85% of the in vivo newly synthesized RNA. In regenerating liver the proportion of the insoluble residual chromatin increases while the radioactivity of the newly synthesized DNA in this fraction is highest. Residual chromatin can be solubilized by ultrasonic treatment only. The Ca2+, Mg2+-dependent dissolving factor is not present either in brain or in PMN leucocyte nuclei.
Mol Biol (Mosk)
PMID:[Solubilization of chromatin by an endogenous enzymic Ca2+, Mg2+-dependent factor. Activity of residual chromatin]. 105 86


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