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

Bovine fibrinogen and the Aalpha and Bbeta chains of bovine fibrinogen have been subjected to chemical modification by a number of reagents and the effects of these procedures on the susceptibility of the proteins to thrombin hydrolysis is described. The reagents used were rose bengal (for photo-oxidation), 2-hydroxy-5-nitrobenzyl bromide, N-acetylimidazole, iodoacetic acid and diethyl pyrocarbonate. Evidence is presented which indicates that the tryptophan and tyrosine residues of fibrinogen are not involved to any great extent in the interaction of this protein with thrombin. Modification with iodoacetic acid suggests that methionine residues play a major role in such interactions, but the fibrinogen chains on which the important residues reside remain uncertain. The use of diethyl pyrocarbonate indicates the participation also of histidine in fibrinogen-thrombin interactions and that, whereas the histidine residues of the Bbeta chain are involved to a great extent, it appears that those of the Aalpha chain are not. The similarities which exist between the fibrinogen-thrombin and the kappa-casein-chymosin systems are discussed.
Mol Cell Biochem 1978 Aug 16
PMID:Characterization of the amino acids of bovine fibrinogen involved in the fibrinogen-thrombin interaction of the blood clotting process. Comparison with the milk clotting process. 36 48

Aminoacyl tRNA synthetases discriminate between tRNA species by a highly specific mechanism. Physical and chemical studies indicate that the synthetases bind along and around the inside of the three-dimensional L-shaped tRNA structure. Studies of mutant tRNAs that affect synthetase interaction tend to confirm this conclusion. However, in contrast to proteins that recognize a specific block of contiguous nucleotide units (e.g., repressors, restriction enzymes, etc.), synthetases appear to interact with spatially disperse elements of the structure. Available evidence suggests that tRNA binding clefts on various synthetases may be roughly similar, with specificity being achieved by the choice of amino acid residues in a few critical positions in the tRNA binding clefts. With this idea in mind, it should be possible to introduce amino acid substitutions into the binding clefts and thereby change tRNA recognition specificity. This has been attempted (by genetic manipulations) and a mutant alanine tRNA synthetase with altered tRNA recognition has been isolated. This enzyme can attach alanine to isoleucine specific tRNA. When presented with valine specific tRNA, a tRNA similar in some structural features to the isoleucine specific tRNA, or with the structurally quite different tyrosine specific tRNA, no significant aminoacylation occurs. Thus, a precise specificity alteration can occur through mutation; this result supports the idea of similarities in synthetase binding clefts, with specificity being achieved by the positioning of amino acids at critical positions in these clefts. Finally, further data have been obtained on the issue of possible transient covalent bond formation between synthetases and tRNAs, as a critical part of the interaction.
Mol Cell Biochem 1979 May 06
PMID:Recent results on how aminoacyl transfer RNA synthetases recognize specific transfer RNAs. 38 92

Studies were undertaken to determine if mitochondrial rRNA synthesis in yeast is regulated by general cellular stringent control mechanism. Those variables affecting the relaxation of a cycloheximide-induced stringent response as a result of medium-shift-down or tyrosine limitation include: 1) the stage of cell growth, 2) carbon source, 3) strain differences and, 4) integrity of the cell wall. The extent of phenotypic relaxation decreased or was eliminated entirely in a strain dependent manner as cells entered stationary phase of growth or by growth of cells on galactose or in osmotically stabilized spheroplast cultures. Cytoplasmic and mitochondrial RNA species were extracted from regrowing spheroplast cultures subjected to different experimental regimens and analyzed by electrophoresis on 2.5% polyacrylamide gels. Relative rates of synthesis were determined in pulse experiments and normalized by double-label procedures to longterm label material. Tyrosine starvation was found to inhibit synthesis of the large and small rRNA species of both cytoplasmic and mitochondrial rRNAs to about 5-20% of the control values. Chloramphenicol inhibits mitochondrial and cytoplasmic rRNA synthesis to 60-80% of control; however, chloramphenicol addition does not relax the stringent inhibition of either class of rRNAs. Cycloheximide addition results in 70-80% inhibition of synthesis of both cellular speceis of rRNAs. As noted above, cycloheximide does not relax the stringent response of cytoplasmic rRNA synthesis in spheroplasts, and also does not relax the stringent inhibition of mitochondrial rRNA synthesis. From these studies, we conclude that both cytoplasmic and mitochondrial rRNA synthesis share common control mechanisms related to regulation of protein synthesis by shift-down or amino acid limitation.
Mol Gen Genet 1979 Jun 20
PMID:Regulation of mitochondrial ribosomal RNA synthesis in yeast. I. In search of a relaxation of stringency. 38 47

The post-translational addition of tyrosine to alpha-tubulin, catalyzed by tubulin:tyrosine ligase, has been previously reported in mammals and birds. The present study demonstrated that significant ligase activity was present in representative organisms from several other major vertebrate classes (chondrichthyes through reptiles) and that both substrate and enzyme from all vertebrates investigated were compatible with mammalian ligase and tubulin in the tyrosination reaction. None of the invertebrate tissues examined showed incorporation of tyrosine, phenylalanine or dihydroxyphenylalanine into alpha tubulin under conditions allowing significant incorporation of these compounds in vertebrate supernatant samples. The failure of invertebrate tubulin to incorporate tyrosine in vitro did not appear to be due to saturation of the carboxyl terminal position with tyrosine or the presence of a soluble inhibitor of ligase activity. Although tubulin amino acid composition has been highly conserved throughout evolution, a major evolutionary divergence is described based upon biochemical differences whereby invertebrate tubulin cannot be tyrosinated or post-translationally modified with phenylalanine or dihydroxyphenylalanine under conditions suitable for the incorporation of these compounds by vertebrate alpha tubulin.
J Mol Evol 1979 Oct
PMID:The phylogenetic distribution of tubulin:tyrosine ligase. 50 46

The fluorescence method was used to reveal some differences in the interaction of gene 5 protein of phage f1 with single- and double-stranded polynucleotides (DNA). The binding with the duplexes is non-cooperative and the Kapp is twice lower than that for the cooperative formation of the complex with single-stranded structures. In the complex with a double-stranded polynucleotide (DNA) the protein cover 3 nucleotide pairs. The complex dissociates with a lower concentration of salt and the contribution of the energy of nonelectrostatic interactions to the total energy of complex formation for it is lower than for the complex with single-stranded DNA. In the complex of protein with single-stranded structure the fluorescence of the tyrosine (Tyr) residues is quenched to a greater degree and their accessibility to the external quencher is lower than that of the complex with double-stranded polynucleotides (DNA). The suggestion is made that in destabilization of nucleic double helices by gene 5 protein of phage f1, a great role belongs to Tyr residues because of their high affinity to single-stranded structures and because of their different localization in the complexes with single- and double-stranded polynucleotides.
Mol Biol (Mosk)
PMID:[Interaction of gene 5 protein of phage f1 with single and double-stranded DNA and polynucleotides]. 50 62

Using quantitative gel filtration techniques partition coefficients, Kp-values, have been determined between aqueous cationic micellar hexadecyltrimethylammonium bromide, CTAB, and several biomonomer. Kp-values for 5'-adenylic acid, 5'-cytidylic acid, 5'-guanylic acid, 5'-uridylic acid and 5'-thymidylic acid are 1,400 +/- 150. Nucleotides bind to CTAB micelles effectively, but nonselectively. Conversely, the binding of tRNAs to micellar CTAB is selective. Kp-values for glutamic acid II, tyrosine and phenylalanine tRNAs (in 1.0MNaCl) are 520, 3,100 and 5,600, respectively. Kp-values for the binding of alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, phenylalanine, serine, threonine and tryptophan to micellar CTAB are less than 8. Conversion of unitless Kp-values for the binding of amino acids, nucleotides and nucleosides to both anionic and cationic micelles, to K (in 1/g) values allows the comparison of clays and micelles as prebiotic concentrating media. Using correlations between surface densities of the biomonomers and their binding constants, it is shown that aqueous micelles (at pH = 8) are a better concentrating media than are clays.
J Mol Evol 1977 Dec 29
PMID:Partitioning of amino acids and nucleotides between water and micellar hexadecyltrimethylammonium halides. The prebiotic significance of cationic surfaces. 59 74

1. Free amino acids were determined in the plasma and in the muscle tissue of 14 patients with chronic uraemia; eight were not on dialysis and six were having regular peritoneal dialysis. The concentration of each amino acid in muscle water was calculated with the chloride method. 2. In both groups of patients there were low intracellular concentrations of threonine, valine, tyrosine and carnosine, and high glycine/valine and phenylalanine/tyrosine ratios. Both groups of patients had increased amounts of 1- and 3-methyl-histidine in plasma and in muscle water. 3. The non-dialysed patients had low intracellular concentrations of lysine, and the dialysed patients had high intracellular concentrations of lysine, isoleucine, leucine and of some of the non-essential amino acids. 4. After peritoneal dialysis for 22 h, the plasma concentration of several amino acids decreased but the intracellular concentrations of most amino acids did not change significantly. 5. Intravenous administration of essential amino acids and histidine during the last 4 h of dialysis increased in muscle the total free amino acids, the ratio of essential to non-essential amino acids and the valine and phenylalanine concentrations. 6. The results demonstrated that the plasma and muscle concentrations of several amino acids are grossly abnormal in chronic uraemia. Non-dialysed and dialysed patients exhibit important differences, especially in the intracellular amino acid patterns. Infusion of essential amino acids may result in enhancement of protein synthesis.
Clin Sci Mol Med 1978 Jan
PMID:Intracellular free amino acids in muscle tissue of patients with chronic uraemia: effect of peritoneal dialysis and infusion of essential amino acids. 62 Apr 93

Residues of Phe, Tyr and Trp in the complexes of their oligonucleotide amidates and polynucleotides of A-U of G-C nucleotide composition are most likely localized in the minor groove of the Watson--Crick part of the triple helix where they interact with bases but do not intercalate into the helix. Formation of the complexes is accompanied with a change in the relative localization of amino acids and bases. The major geometrical parameters of the triple helices of the complexes are not changed by the residues of aromatic amino acids (according to CD data). A slight violation of stacking interactions between bases is observed along with an increase of the cooperativity of melting of the complexes of A-U composition (according to UV absorption data). The effect of the residues of aromatic amino acids on the stability of triple helices is determined by the nucleotide composition of the latter, i.e. complexes of A-U composition are destabilized with the Phe, Tyr and Trp residues, whereas the Trp residue does not affect the stability of the complexes of G-C composition. The hydrophobic character of aromatic amino acids and their different affinity for bases of different structure seem to account for this difference in stability. The dependence of the thermal stability of RNH-dp(An).2poly(U)-complexes on the structure of the amide radical (residues of glycin, aromatic amino acids, alkyl- and arylalkyl amines) testifies the ability of the radical to "regulate" the interaction between the oligomer and the complementary polynucleotide. This capacity for "regulation" is not observed in the system of G-C composition.
Mol Biol (Mosk)
PMID:[Several properties of complexes of polynucleotides with aromatic amino acid amides of oligonucleotides]. 65 81

The kinetics of the affinity modification of phenylalanyl-tRNA synthetase from E. coli MRE-600 with chb-tRNA was used for investigation of copling between the binding sites of tRNA and other ligands. It was shown that ATP, phenylalanine and their mixture do not change the efficiency of complex formation but decrease specifically the rate of enzyme alkylation. L-Tyrosine and L-valine do not influence the enzyme alkylation. ATP is more effective protector than L-phenylalanine. In the presence of both ATP and phenylalanine the enzyme alkylation is excluded. The possibilities of this method for studying the coupling between binding sites are discussed.
Mol Biol (Mosk)
PMID:[Affinity modification of phenylalanyl-tRNA-synthetase in the presence of ligands]. 77 90

By modifying four tyrosine residues in pepsin a derivative (aminopepsin) is obtained which is capable to conjugate with a fluorescent label DNS-Cl without loss of the catalytic activity. Rotational relaxation times of native pepsin and dansylated aminopepsin (DAP) are measured by a fluoresence polarization method. The values obtained are shown to be lower than those calculated for arigid pepsin globule. Possible sources of the obtained difference are discussed. A reversible or covalent blocking of pepsin or DAP active centres by specific inhibitors leads to an increase in rotational relaxation time values for these proteins reaching the magnitude which is very close to that calculated for a model of rigid pepsin. Brownian relaxation of pepsin and DAP reduced by beta-mercaptoethanol and of pepsinogen and some fragments of pepsine macromolecule in aqueous solutions is invigated as well. The results are intepreted as representing an intramolecular mobility or segmental flexibility of pepsin and DAP. With the use of the obtained and X-ray data a segmental model of dynamic pepsin structure is suggested. On the basis of this model some conclusions are drawn concerning a localization of a polypeptide which is split off from the N-terminus of pepsinogen during its activation. A possible role of segmental flexibility in the catalytic action of pepsin is considered.
Mol Biol (Mosk)
PMID:[Intramolecular mobility of pepsin]. 78 36


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