Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An adenosine(5')tetraphospho(5')adenosine (Ap4A) binding protein has been purified from calf thymus. The protein is comprised of a single polypeptide of Mr 54000 and is capable of high-affinity (Kd = 13 microM) binding of Ap4A with great substrate specificity. The Ap4A binding protein has been isolated in two forms: a 'free', or non-polymerase-bound, form which predominates, and a similar form which copurifies with DNA polymerase alpha, but which can be resolved from it. The free form of Ap4A binding protein contains associated adenosine(5')tetraphospho(5')adenosine phosphohydrolase (Ap4Aase) activity, while the form resolved from DNA polymerase alpha contains no such activity. The Ap4Aase activity, which catalyzes the phosphohydrolysis of Ap4A to ATP and AMP, is strongly inhibited by low levels (50-100 microM) of Zn2+ without any effect on the Ap4A binding protein activity. This difference in associated Ap4Aase activity between free and polymerase-bound forms of the protein, plus the copurification mentioned above, indicate a specific association between Ap4A binding protein and DNA polymerase alpha.
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PMID:Adenosine(5')tetraphospho(5')adenosine-binding protein of calf thymus. 669 19

The exocellular beta-lactamase (penicillin amido-beta-lactamhydrolase, EC 3.5.2.6) of Actinomadura R39 consists of one single polypeptide chain of molecular weight about 15 200. It exhibits a highly asymmetrical shape, has a low isoelectric point (at pH 5.0) and contains about 9.3% (w/w) of a polydeoxyribonucleotide with which it forms a rather stable complex. Removal of a substantial amount of this deoxyribonucleotide by treatment with DNAase I has no effect on the enzyme activity. The beta-lactamase has a wide spectrum of activity. Penicillins and delta 3-cephalosporins can be either good or poor substrates. Oxacillin, which is a poor substrate of most beta-lactamases from Gram-positive bacteria, is a good substrate of the beta-lactamase of Actinomadura R39. Its best substrate, however, is nitrocefin (kcat/Km: 2300 000 M-1.s-1; catalytic centre activity: 210 s-1). The kcat/Km values observed with some penicillins and delta 3-cephalosporins are similar to the values of the bimolecular rate constants that govern the formation of the acyl-enzyme intermediates between these antibiotics and the serine D-alanyl-D-alanine peptidase that is also secreted by the same strain Actinomadura R39. Such a relationship, however, is not observed with all the beta-lactam compounds tested.
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PMID:Purification and properties of the exocellular beta-lactamase of Actinomadura strain R39. 697 97

A monoclonal antibody (mAb) KSm2 and three human Sm sera, which detect the 'D' polypeptide in mammals and is associated with the U1, U2, U4/U6, U5, U7, U9-U12 small nuclear RNAs, have been used in Western blotting to show that the antigen is conserved in wheat (Triticum aestivum cv. Beaver). Immunocytochemistry to wheat and a barley (Hordeum vulgare) suspension culture using the mAb KSm2 has shown that the 'D' polypeptide occurs in interphase nuclei as speckles and foci outside the nucleoli and as tracks. Nucleoli usually had at least one focus at their periphery. Immunocytochemistry at the electron microscope level of resolution has shown that the signal occurs between chromatin axes and predominantly in the outer domain of the nucleus. Analysis of the barley suspension culture demonstrated that there was a significant increase in antigen through G1, S to G2. In the wheat meristematic cells at prophase only the foci remained, and at metaphase the distribution of foci was asymmetrical with foci occurring either at one pole or on the metaphase plate. At telophase the foci appeared to decrease in size and were incorporated non-uniformly into the daughter nuclei because of their asymmetric distribution at metaphase. When wheat was grown at a range of temperatures, the root tip meristematic nuclei showed a number of different organization patterns. The average number of nucleoli increased and their size decreased. At the same time there was an increase in the average total area of foci as temperature increased from 4 degrees, 10 degrees, 25 degrees, 34 degrees, to 37 degrees C. Thus the 'D' polypeptide distribution changes with metabolic activity and through the cell cycle.
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PMID:The distribution of a spliceosome protein in cereal (Triticeae) interphase nuclei from cells with different metabolic activities and through the cell cycle. 749 99

The synaptic organization of nerve terminals containing calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), substance P (SP) and enkephalin (ENK) in the intralaryngeal local ganglia of the cat was investigated by immunoelectron microscopy. CGRP-immunoreactive (IR) and VIP-IR varicose fibers formed mainly axo-dendritic synapses, whereas SP-IR and ENK-IR varicose fibers made axo-somatic synapses to the principal neurons of the local ganglion. The synaptic specializations of the CGRP-IR varicosities were asymmetrical, or Gray's type I, whereas the other peptide-IR varicosities showed symmetrical, or Gray's type II, synaptic specializations. After denervation of the extrinsic nerves, CGRP-IR varicose fibers disappeared from the ganglion, but VIP-IR, SP-IR and ENK-IR varicose fibers and synapses remained. These results suggest that local ganglia act as an integration center of laryngeal function rather than as a unidirectional parasympathetic relay center.
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PMID:Immunoelectron microscopic studies of synaptic organization in the intralaryngeal ganglia of the cat. 750 65

The Escherichia coli chaperonin GroEL and its regulator GroES are thought to mediate adenosine triphosphate-dependent protein folding as an asymmetrical complex, with substrate protein bound within the GroEL cylinder. In contrast, a symmetrical complex formed between one GroEL and two GroES oligomers, with substrate protein binding to the outer surface of GroEL, was recently proposed to be the functional chaperonin unit. Electron microscopic and biochemical analyses have now shown that unphysiologically high magnesium concentrations and increased pH are required to assemble symmetrical complexes, the formation of which precludes the association of unfolded polypeptide. Thus, the functional significance of GroEL:(GroES)2 particles remains to be demonstrated.
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PMID:Functional significance of symmetrical versus asymmetrical GroEL-GroES chaperonin complexes. 763

The chaperonins GroEL and GroES of Escherichia coli facilitate protein folding in an adenosine triphosphate (ATP)-dependent reaction cycle. The kinetic parameters for the formation and dissociation of GroEL-GroES complexes were analyzed by surface plasmon resonance. Association of GroES and subsequent ATP hydrolysis in the interacting GroEL toroid resulted in the formation of a stable GroEL:ADP:GroES complex. The complex dissociated as a result of ATP hydrolysis in the opposite GroEL toroid, without formation of a symmetrical GroEL:(GroES)2 intermediate. Dissociation was accelerated by the addition of unfolded polypeptide. Thus, the functional chaperonin unit is an asymmetrical GroEL:GroES complex, and substrate protein plays an active role in modulating the chaperonin reaction cycle.
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PMID:Asymmetrical interaction of GroEL and GroES in the ATPase cycle of assisted protein folding. 763 1

An asymmetrically-cleaving diadenosine 5',5"'-P1,P4-tetraphosphate hydrolase (Ap4A-->ATP+AMP) is present in all higher eukaryotes and contributes to the regulation of the intracellular level of the alarmone nucleotide diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A). This enzyme has previously been isolated from unfractionated human blood cells. The aim of this report is to determine the contribution made by different blood cell types as part of our study of the roles of Ap4A as an intra- and extracellular signalling molecule. Ap4A hydrolase was partially purified from isolated human erythrocytes, leukocytes and platelets by high performance gel permeation chromatography and characterized by kinetic analysis and by probing immunoblots with an antibody raised against the human placental enzyme. Ap4A hydrolase was clearly present in all three cell types. Each enzyme comprised a single polypeptide of M(r) 19,200. The erythrocyte and platelet enzymes had a Km for Ap4A of 0.70 +/- 0.05 microM (n = 3) while the Km for the leukocyte enzyme was 1.50 +/- 0.20 microM (n = 3). All three enzymes showed substrate inhibition above 10 microM Ap4A. The specific activity of the enzyme in erythrocytes was 0.067 U/10(6) cells, 15-fold lower than that in leukocytes and platelets. However, the erythrocyte hydrolase accounted for 97% of the total activity of unfractionated blood cells (336 U out of 346 U/ml blood). The study shows that leukocytes, platelets and erythrocytes all contain Ap4A hydrolase activity. The last observation is of particular interest given the reported absence of Ap4A from enucleated erythrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Diadenosine 5',5"'-P1,P4-tetraphosphate hydrolase is present in human erythrocytes, leukocytes and platelets. 776 87

The enzyme diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) pyrophosphohydrolase has been purified to homogeneity from firefly lanterns. It is a single polypeptide of M(r) 16,000 with a Km for Ap4A of 1.9 microM and kcat = 3.6 s-1. It is inhibited competitively by adenosine 5'-tetraphosphate (Ki = 7.5 nM) and non-competitively by fluoride ions (Ki = 50 microM). The specific activity of the enzyme in crude extracts of at least 20 milliunits/mg protein is 10-100 times higher than in any other eukaryote so far examined. Interestingly, firefly luciferase is known to synthesize Ap4A and related adenine-containing dinucleoside tetraphosphates in vitro. The high activity of Ap4A hydrolase in lanterns may be related to this ability and could be relevant to the use of the luciferase gene as a reporter gene.
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PMID:Lanterns of the firefly Photinus pyralis contain abundant diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase activity. 787 10

The DNA methyltransferases of type I restriction-modification systems are trimeric enzymes composed of one DNA specificity (S) subunit and two modification (M) subunits. The S subunit contains two large regions, each of which recognizes one part of the split, asymmetrical DNA target sequence. Each M subunit contains an amino acid motif for binding the methyl group donor and cofactor, S-adenosyl methionine. The EcoKI methyltransferase has a strong preference for methylating a hemimethylated DNA target rather than an unmodified target. We have used partial proteolytic digestion of EcoKI methyltransferase to generate polypeptide domains that we have identified by amino acid sequencing. The S subunit was cut into two large, folded domains each containing one DNA binding region. Binding of DNA partially protected the S subunit from digestion. The M subunit was also cut into two large domains joined together by a short flexible loop, and a C-terminal tail region. The short loop contained part of the S-adenosyl methionine binding motif, and cofactor binding protected the loop and the two large domains from proteolysis. The C-terminal domain of M remained associated with the N-terminal domain of the S subunit even after the rest of the protein had been digested. The conformation of the tail region of the M subunit was sensitive to the methylation state of DNA in ternary complexes also containing S-adenosyl methionine, and could differentiate between unmethylated and hemimethylated DNA substrates.
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PMID:The domains of a type I DNA methyltransferase. Interactions and role in recognition of DNA methylation. 812 Aug 83

We have characterized a novel mutant of EcoDXXI, a type IC DNA restriction and modification (R-M) system, in which the specificity has been altered due to a Tn5 insertion into the middle of hsdS, the gene which encodes the polypeptide that confers DNA sequence specificity to both the restriction and the modification reactions. Like other type I enzymes, the wild type EcoDXXI recognizes a sequence composed of two asymmetrical half sites separated by a spacer region: TCA(N7)RTTC. Purification of the EcoDXXI mutant methylase and subsequent in vitro DNA methylation assays identified the mutant recognition sequence as an interrupted palindrome, TCA(N8)TGA, in which the 5' half site of the wild type site is repeated in inverse orientation. The additional base pair in the non-specific spacer of the mutant recognition sequence maintains the proper spacing between the two methylatable adenine groups. Sequencing of both the wild type and mutant EcoDXXI hsdS genes showed that the Tn5 insertion occurred at nucleotide 673 of the 1221 bp gene. This effectively deletes the entire carboxyl-terminal DNA binding domain which recognizes the 3' half of the EcoDXXI binding site. The truncated hsdS gene still encodes both the amino-terminal DNA binding domain and the conserved repeated sequence that defines the length of the recognition site spacer region. We propose that the EcoDXXI mutant methylase utilizes two truncated hsdS subunits to recognize its binding site. The implications of this finding in terms of subunit interactions and the malleability of the type I R-M systems will be discussed.
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PMID:Macroevolution by transposition: drastic modification of DNA recognition by a type I restriction enzyme following Tn5 transposition. 822 68


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