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

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly(U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly(U). At pH 7.1, transfer to poly(U) was five times as great as to poly(A) and transfer to a poly(A) poly(U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly(U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2' hydroxyl groups throughout poly(U) and the 2' (3') hydroxyl groups at the terminus of poly(U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
J Mol Evol 1975 Dec 29
PMID:Aminoacyl transfer from an adenylate anhydride to polyribonucleotides. 0 44

The molecule of type I collagen from skin consists of two alpha1(I)-chains and one alpha2-chain. The sequence of the entire alpha1-chain comprising 1052 residues is summarily presented and discussed. Apart from the 279 residues of alpha1(I)-CB8 whose sequence has been established for rat skin collagen, all sequences have been determined for calf skin collagen. In order to facilitate sequence analysis, the alpha1-chain was cleaved into defined fragments by cyanogen bromide or hydroxylamine or limited collagenase digestion. Most of the sequence was established by automated stepwise Edman degradation. The alpha1-chain contains two basically different types of sequences: the triple helical region of 1011 amino acid residues in which every third position is occupied by glycine and the N- and C-terminal regions not displaying this type of regularity. Both of these non-triple helical regions carry oxidizable lysine or hydroxylysine residues as functional sites for the intermolecular crosslink formation. Implications of the amino acid sequence for the stability of the triple helix and the fibril as well as for formation of crosslinks are discussed. Evaluation of the sequence in connection with electron microscopical investigations yielded the parameters of the axial arrangement of the molecules within the fibrils. Axial stagger of the molecules by a distance D = 670 angstrom = 233 amino acid residues results in maximal interaction of polar sequence regions of adjacent molecules and similarly of regions of hydrophobic residues. Ordered aggregation of molecules into fibrils is, therefore, regulated by electrostatic and electrophobic forces. Possible loci of intermolecular crosslinks between the alpha1-chains of adjacent molecules may be deduced from the dimensions of the axial aggregation of molecules.
Mol Cell Biochem 1975 Sep 30
PMID:Information contained in the amino acid sequence of the alpha1(I)-chain of collagen and its consequences upon the formation of the triple helix, of fibrils and crosslinks. 17 54

Chemical modification of pig heart ferricytochrome C by the paramagentic analog of N-acetylimidazole-N-(2,2',5,5'-tetramethyl-3-carboxypyrroline-1-oxyl)-imidazole has been studied. Two main modified preparations, both with the single spin label per molecule, have been isolated by means of chromatography on CM-Sephadex C-25. The study of UV-difference spectra of the SL-preparations versus native Cyt C, the spectrophotometric titration of the tyrosine residues in modified proteins and the study of their reaction with hydroxylamine allow to conclude that one of these preparations (fraction II) is lysine modified Cyt C-SL(Lys)-Cyt C and the other (fraction III) is tyrosine modified protein-SL(Tyr)-Cyt C. From the present results and the data available in literature the most probable location of the modification sites in the three-dimentional structure of Cyt C is Tyr-74 in SL (Tyr)-Cyt C and one of the neighbouring lysil residues Lys 72 or Lys 73 in SL (Lys)-Cyt C on the molecular surface. From the absorbtion and CD-spectra of the modified and native Cyt C in the spectral interval 190--450 nm and from the high resolution PMR data the conclusion has been made that the chemical modification does not alter the immediate vicinity of the heme group and the molecular structure of Cyt C as a whole. Therefore both SL-modified preparations might be useful for the conformational and functional investigations of Cyt C.
Mol Biol (Mosk)
PMID:[Chemical modification of ferricytochrome c by N-(2,2',5,5'-tetramethyl-3-carboxypyrroline-1-oxyl)-imidazole]. 21 5

Hydroxylamine was used to induce mutants of the ColE1 derived plasmid pML2 that are inefficiently mobilized (Mob-) during conjugation by an Hfr donor. The ability of those mutants to be complemented by deletion mutants and Tn3 insertion mutants of ColE1 was examined. Three complementation groups were identified and localized on the ColE1 genetic map (Mob1, Mob2, and Mob3). One hydroxylamine mutant was not complemented by any mobilization deficient mutant but was complemented by mobilizable ColE1 mutants. Two hydroxylamine mutants were not complemented by any ColE1 derivatives. A mutant that had its relaxation nick site deleted had a markedly reduced mobilizability. The relationship between DNA relaxation nick site deleted had a markedly reduced mobilizability. THe relationship between DNA relaxation, replication and mobilization is considered.
Mol Gen Genet 1979 May 04
PMID:A complementation analysis of mobilization deficient mutants of the plasmid ColE1. 22 40

Mutagenesis by 5-bromouracil of lambda phage to clear plaque formers does not depend on the recA function of the host E. coli cell or on the red function of the phage. Pretreatment of the host cells with ultraviolet light does not affect bromouracil mutagenesis of the adsorbed phage. Mutagenesis by hydroxlamine to clear plaque formers takes place at a high level in recA- host cells, and is not changed by preirradiation of of rec+ (wild type) hosts with ultraviolet light. Thus, bromouracil and hydroxylamine appear to mutate lambda phage by a process which differs from that responsible for ultraviolet mutagenesis. Two characteristics of bromouracil mutagenesis--the nonlinear dependence of the number of mutants on bromouracil incorporation, and a high frequency of heterozygotes--fit in with Rydberg's (1977) picture of bromouracil mutagenesis as a consequence of base mispairing, with mismatch repair removing the mutations at low incorporation of the analog.
Mol Gen Genet 1977 Mar 28
PMID:Mutagenesis of lambda phage: 5-bromouracil and hydroxylamine. 32 84

E. coli DNA dependent RNA polymerase was modified by diethylpyrocarbonate. Optical and kinetic properties of the reaction were studied. More than 90% of RNA polymerase activity is inhibited by introduction of 9--11 ethoxyformyl groups per enzyme molecule without loss of its ability to bind DNA template. Furthermore the modified enzyme is able to form tight complexes with DNA and to compete with native enzyme for the formation of rifampicin-resistant complex. The ratio of the complex formation constants for the native and modified enzyme was determined to be equal to 10. The enzyme modified to such extent loses the activity in DNA dependent RNA as well as pppApU synthesis. Vmax value rather than Km value for both ATP and UTP decreases following the modification reaction. Incubation of the enzyme modified to the 10% of residual activity with 0.2 M hydroxylamine for 2 hours results in restoration of RNA polymerase activity. Most but not all of the modified histidyl residues restore their native structure. Two of 13 histidyl residues were modified irreversibly due to Bamberger's cleavage reaction, but these two residues were found to be unessential for RNA polymerase activity. Reaction with higher concentration of the diethylpyrocarbonate induces modification of more than 15--20 histidyl residues and leads to irreversible inactivation of the enzyme. Nevertheless the modification of the additional histidyl redidues was reversible as well as the modification of the first 11 residues. RNA polymerase modified to such extent loses the ability to bind DNA. Preformation of the initiated ternary complex of RNA polymerase with template and product fails to protect the enzyme from reversible inactivation at a low reagent concentration, but markedly decreases the rate of the irreversible and unspecific modification of sulfhydryl or amino groups of the enzyme. Reaction with the ternary complex results in reversible inactivation of the enzyme with respect to elongation of RNA chains as well as the pyrophosphate exchange reaction. The complex itself was, however, completely stable under the reaction conditions and the enzyme subunit structure was also conserved after the reaction. Evidently, the mild modification of the histidyl residues with diethylpyrocarbonate selectively inhibits RNA chain elongation.
Mol Biol (Mosk)
PMID:[Modification of the RNA-polymerase of Escherichia coli by diethylpyrocarbonate]. 37 63

Kinetic parameters of photoinduced permeability increase of artificial lipid membranes, modified by ROS fragments (tau20 degrees C = 20 mesec Ea = 33 +/- 2 kcal/mole) coincides with appropriate parameters of photoinduced protein fluorescence intensity decrease and ROS fragments absorption spectra change (metarhodopsin I leads leads to metarhodopsin II transition). Hydroxylamine accelerates this process, its rate is proportional to hydroxylamine at concentrations lower than 0.6 M.
Mol Biol (Mosk)
PMID:[Molecular mechanisms of receptor. II. Identification of the conformational transition of rhodopsin responsible for the leading edge of the photoresponse of artificial lipid membranes modified by fragments of the outer segment of rods]. 61 19

The kinetics of photoinduced changes of protein fluorescence of cattle visual pigment was studied in the presence of hydroxylamine. The rate constant of fluorescence increase is proportional to NH2OH concentration when it is less than 0.4 M. It reaches the maximal magnitude (3.3 +/- 1 sec-1) at higher hydroxylamine concentration. Fluorescence increase rate is controlled by the rate of chemical reaction of rhodopsin with hydroxylamine. It is limited by conformational rearrangement of opsin. This rearrangement does not induce absorbance spectrum change of visual pigment, but confers to it the capability to react with NH2OH and NaBH4. Kinetic parameters of this rearrangement (tau 20 degrees C approximately 300 msec, Eact = 19 +/- 2 kcal/mole) coincide with kinetic parameters of diminishing of the photoresponse of artificial lipid membrane modified by fragments of rod outer segments in the temperature range studied (+2 divided by +25 degrees C).
Mol Biol (Mosk)
PMID:[Molecular mechanisms of receptor-potential generation by the photoreceptor. III. Conformational transition responsible for the tail end of the photoresponse of an artificial lipid membrane modified by fragments of the external segments of rods]. 61 34

An investigation of in vitro mutagenesis of plasmid DNA with hydroxylamine is described. The treated plasmid DNA was used to transform Escherichia coli K12. Mutants of the plasmid NTP3, which codes for resistance to ampicillin and sulphonamides, were isolated and characterised. They were classified according to the reduction in level of their beta-lactamase activity. Hydroxylamine-induced mutants of NTP14 were also isolated. This plasmid codes for ampicillin resistance, synthesis of colicin E1, and the EcoRI restriction and modification enzymes. One class of mutants is lethal to the host strain at temperatures above 33 degrees C, but carrier strains grow well at 28 degrees C. There is evidence that these mutants code for a temperature-sensitive EcoRI modification activity: the lethal effect probably results from the cleavage of the host-cell DNA by the restriction enzyme at non-permissive temperatures. The possible genetic uses of the mutant plasmids for the production of hybrid plasmids in the bacterial cell are discussed.
Mol Gen Genet 1976 Apr 23
PMID:Mutagenesis of plasmid DNA with hydroxylamine: isolation of mutants of multi-copy plasmids. 77 4

Recently it has been demonstrated that hydroxylamine is an activator of triglyceride catabolism. We have studied the effect of hydroxylamine on isocitrate lyase activity and lipid catabolism and have noted a stimulation of isocitrate lyase biosynthesis by 5 mM hydroxylamine. The specificity of this effect was tested with a number of representative enzymes of other metabolic pathways. In an attempt to study the possible mechanism of action of hydroxylamine we have also tested the effects of two substances that are structural or functional analogues of hydroxylamine, namely, ethanolamine and hydrazine, both on the enzyme level in plant cultures and on the activity of enzyme preparations. From our data we may conclude that "de nove" biosynthesis of isocitrate lyase depends on the reaction of hydroxylamine or hydrazine with glyoxylate to give the corresponding oxime and hydrazone. The removal of glyoxylate from the biological equilibrium in this way could cause extra formation of isocitrate lyase.
Mol Cell Biochem 1977 Apr 12
PMID:Stimulation of isocitrate lyase biosynthesis by hydroxylamine and hydrazine. 89 30


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