101
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Laloux I, Jacobs E, Dubois E. Involvement of SRE element of Ty1 transposon in TEC1-dependent transcriptional activation. Nucleic Acids Res 1994; 22:999-1005. [PMID: 8152932 PMCID: PMC307921 DOI: 10.1093/nar/22.6.999] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Some Ty1 transposable element insertion mutations of Saccharomyces cerevisiae activate transcription of adjacent genes in a cell-type dependent manner. This activation requires at least STE12 and TEC1 gene products. The binding site for the STE12 protein is located in the sterile responsive element (SRE), which is just downstream the 5' LTR of Ty1 and contains one copy of the pheromone response element (PRE). This report defines the sequences in Ty1 required for TEC1-dependent activation using a TDH3::lacZ reporter gene in which the UAS was replaced by different portions of a Ty1 or Ty2 element. The Ty1 SRE seems to be sufficient to ensure the TEC1 and STE12-mediated activation whereas Ty2 SRE can activate the expression of the adjacent genes in the absence of both proteins. Adjacent to the PRE element, there is a region (PAE) with extensive sequence divergence in Ty1 and Ty2 SREs. Swapping experiments between Ty1 and Ty2 sequences show that Ty1 PAE is required for the activation of adjacent gene expression in a TEC1 and STE12-dependent manner. The use of a LexA::TEC1 construct indicates that the chimeric protein has no activation ability suggesting that TEC1 could act in conjunction with another factor.
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Affiliation(s)
- I Laloux
- Laboratoire de Microbiologie, Université Libre de Bruxelles, Belgium
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102
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Dhalla AM, Li B, Alibhai MF, Yost KJ, Hemmingsen JM, Atkins WM, Schineller J, Villafranca JJ. Regeneration of catalytic activity of glutamine synthetase mutants by chemical activation: exploration of the role of arginines 339 and 359 in activity. Protein Sci 1994; 3:476-81. [PMID: 7912599 PMCID: PMC2142696 DOI: 10.1002/pro.5560030313] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In order to understand the nature of ATP and L-glutamate binding to glutamine synthetase, and the involvement of Arg 339 and Arg 359 in catalysis, these amino acids were changed to cysteine via site-directed mutagenesis. Individual mutations (Arg-->Cys) at positions 339 and 359 led to a sharp drop in catalytic activity. Additionally, the Km values for the substrates ATP and glutamate were elevated substantially above the values for wild-type (WT) enzyme. Each cysteine was in turn chemically modified to an arginine "analog" to attempt to "rescue" catalytic activity by covalent modification; 2-chloroacetamidine (CA) (producing a thioether) and 2,2'-dithiobis (acetamidine)(DTBA) (producing a disulfide) were the reagents used to effect these chemical transformations. Upon reaction with CA, both R339C and R359C mutants showed a significant regain of catalytic activity (50% and 70% of WT, respectively) and a drop in Km value for ATP close to that for WT enzyme. With DTBA, chemically modified R339C had a greater kcat than WT glutamine synthetase, but chemically modified R359C only regained a small amount of activity. Modification with DTBA was quantitative for each mutant and each modified enzyme had similar Km values for both ATP and glutamate. The high catalytic activity of DTBA-modified R339C could be reversed to that of unmodified R339C by treatment with dithiothreitol, as expected for a modified enzyme containing a disulfide bond. Modification of each cysteine-containing mutant to a lysine "analog" was accomplished using 3-bromopropylamine (BPA).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A M Dhalla
- Department of Chemistry, Pennsylvania State University, University Park 16802
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103
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Felsenstein KM, Hunihan LW, Roberts SB. Altered cleavage and secretion of a recombinant beta-APP bearing the Swedish familial Alzheimer's disease mutation. Nat Genet 1994; 6:251-5. [PMID: 8012386 DOI: 10.1038/ng0394-251] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Mutations within the beta-amyloid precursor protein gene cosegregate with the early-onset form of familial Alzheimer's Disease (FAD). It is not known how these mutations result in disease; however, one early-onset AD mutation in a Swedish kindred increases potentially amyloidogenic fragments and beta-protein production in cells expressing the mutant beta-APP. Using a novel recombinant reporter system we found a qualitative change in the secreted product, from cleavage within the beta-protein sequence to cleavage near the N-terminal region of the beta-protein, even though the total amount of secreted mutant product is similar to wild-type. The results suggest that the increased formation of potentially amyloidogenic fragments in cells expressing the Swedish FAD occurs by enzymatic cleavage in the secretory pathway. Alterations in the secretory process may predispose an individual to AD.
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Affiliation(s)
- K M Felsenstein
- CNS-Department of Biophysics and Molecular Biology, Bristol-Myers Squibb, Pharmaceutical Research Institute, Wallingford, Connecticut 06492
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104
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Zhang ZY, Wang Y, Dixon JE. Dissecting the catalytic mechanism of protein-tyrosine phosphatases. Proc Natl Acad Sci U S A 1994; 91:1624-7. [PMID: 8127855 PMCID: PMC43215 DOI: 10.1073/pnas.91.5.1624] [Citation(s) in RCA: 200] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Protein-tyrosine phosphatases (PTPases) contain an evolutionarily conserved segment of 250 amino acids referred to as the PTPase catalytic domain. The recombinant PTPase domain from Yersinia enterocolitica enhances the rate of hydrolysis of p-nitrophenyl phosphate, a phosphate monoester, by approximately 10(11) over the non-enzyme-catalyzed rate by water. Specific amino acid residues responsible for the catalytic rate acceleration have been examined by site-directed mutagenesis. Our results suggest that Asp-356 (D356) and Glu-290 (E290) are the general acid and the general base catalysts responsible for Yersinia PTPase-catalyzed phosphate ester hydrolysis. The PTPase with both E290Q and D356N mutations shows no pH dependence for catalysis but displays a rate enhancement of 2.6 x 10(6), compared to the noncatalyzed hydrolysis of p-nitrophenyl phosphate by water. This rate enhancement probably occurs via transition-state stabilization. Our results suggest that all PTP-ases use a common mechanism that depends upon formation of a thiol-phosphate intermediate and general acid-general base catalysis.
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Affiliation(s)
- Z Y Zhang
- Department of Biological Chemistry, Medical School, University of Michigan, Ann Arbor 48109-0606
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105
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Franks RG, Crews ST. Transcriptional activation domains of the single-minded bHLH protein are required for CNS midline cell development. Mech Dev 1994; 45:269-77. [PMID: 8011558 DOI: 10.1016/0925-4773(94)90013-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The single-minded gene functions as a master developmental regulator within the midline cell lineage of the embryonic central nervous system of Drosophila melanogaster. Genetic experiments suggest that Single-minded can function as a transcriptional activator. Regions of the Single-minded protein were fused to the DNA binding domain of the mammalian transcription factor Sp1 and shown to activate transcription from a reporter gene linked to Sp1 binding sites. Three independent activation domains were identified in the carboxy terminal region of Single-minded that include areas rich in serine, threonine, glutamine and proline residues. Germ line transformation experiments indicate that the carboxy terminal activation domains, the PAS dimerization domain, and the putative DNA binding basic domain of Single-minded are required for expression of CNS midline genes in vivo. These results define in vivo a functional activation domain within Single-minded and suggest a model in which Single-minded activates transcription through a direct interaction with promoter elements of CNS midline genes.
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Affiliation(s)
- R G Franks
- Molecular Biology Institute, University of California, Los Angeles 90024
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106
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Gettins PG, Boel E, Crews BC. Thiol ester role in correct folding and conformation of human alpha 2-macroglobulin. Properties of recombinant C949S variant. FEBS Lett 1994; 339:276-80. [PMID: 7509297 DOI: 10.1016/0014-5793(94)80430-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To determine the role of the thiol ester in the folding of human alpha 2-macroglobulin (alpha 2M) in the active conformation, we have characterized a recombinant variant of alpha 2M, C949S, expressed in baby hamster kidney cells, that lacks the thiol ester-forming cysteine. C949S alpha 2M behaves like methylamine-treated plasma alpha 2M, with correctly formed inter-subunit disulfide bridges, non-covalent association of covalent dimers to form tetramers, and exposure of the receptor binding domain, but an inability to inhibit proteinases, and inaccessibility of the bait regions to proteolysis. We concluded that correct folding of monomers or their association to give tetrameric alpha 2M does not require a pre-formed thiol ester. Active alpha 2M may form in vivo by a two-step process involving initial folding to give a structure resembling that of C949S alpha 2M followed by thiol ester formation and a conformational change that gives the native active state.
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Affiliation(s)
- P G Gettins
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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107
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Caspari T, Stadler R, Sauer N, Tanner W. Structure/function relationship of the Chlorella glucose/H+ symporter. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41890-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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108
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109
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Robertson D, Hilton S, Wong K, Koepke A, Buckley J. Influence of active site and tyrosine modification on the secretion and activity of the Aeromonas hydrophila lipase/acyltransferase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42147-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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110
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111
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Serrano M, Gutiérrez C, Freire R, Bravo A, Salas M, Hermoso JM. Phage phi 29 protein p6: a viral histone-like protein. Biochimie 1994; 76:981-91. [PMID: 7748942 DOI: 10.1016/0300-9084(94)90023-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Phage phi 29 protein p6 is one of the most abundant viral proteins in phi 29-infected B subtilis cells, constituting about 4% of the total cellular proteins (about 3 x 10(6) copies/cell) at late infection. Electron microscopic studies showed that, in vitro, protein p6 forms heterogeneously-sized complexes all along phi 29 DNA, suggesting that protein p6 may have a role in genome packaging and organization. The low stability of the protein p6-phi 29 DNA complexes observed in vitro could reflect the dynamic nature of these complexes, to allow replication, transcription, and encapsidation of the genome. The protein p6-DNA complex consists of a DNA right-handed superhelix wrapped around a multimeric protein core. The DNA in this complex is strongly distorted and compacted. Protein p6 recognition signals have been mapped near the ends of the linear phi 29 DNA and act as nucleation sites for complex formation. Protein p6 does not recognize a specific sequence, but sequences with specific bendable properties that would favor the formation of the complex. Protein p6 represses transcription from the phi 29 C2 early promoter, and activates initiation of phi 29 DNA replication that occurs from both DNA ends. The formation of nucleoprotein complexes at the origins of replication, as well as the specific positioning of protein p6 with respect to the DNA ends are required for the activation of replication. This suggests that the proteins involved in the initiation step of phi 29 DNA replication, either directly interact with protein p6, or recognize a conformational change at a specific location in the DNA. The mechanism of activation could be the local and transient unpairing of DNA at specific sites, facilitated by the strong distortion of DNA conformation in the nucleoprotein complex.
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Affiliation(s)
- M Serrano
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
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112
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Pansegrau W, Schröder W, Lanka E. Concerted action of three distinct domains in the DNA cleaving-joining reaction catalyzed by relaxase (TraI) of conjugative plasmid RP4. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42011-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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113
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Graham LD, Gillies FM, Coggins JR. Over-expression of the yeast multifunctional arom protein. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1216:417-24. [PMID: 8268222 DOI: 10.1016/0167-4781(93)90009-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The pentafunctional arom protein of Saccharomyces cerevisiae is encoded by the ARO1 gene. Substantial elevation of the levels of the arom protein (25-fold) was achieved in yeast using a vector that exploited the ubiquitin-fusion cleavage system of yeast. However, attempts to express the N-terminal 3-dehydroquinate synthase domain (E1) or the internal 3-dehydroquinase domain (E2) using the same system did not succeed. The yeast arom protein was successfully purified from the over-expressing transformant, and was found to possess all five enzymatic activities in a ratio similar to that observed in crude cell extracts. The purified material consisted mainly of a polypeptide that co-migrated in SDS-PAGE with intact arom proteins from other species.
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Affiliation(s)
- L D Graham
- Department of Biochemistry, University of Glasgow, Scotland, UK
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114
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Peterson JA, Myers AM. Functional analysis of mRNA 3' end formation signals in the convergent and overlapping transcription units of the S. cerevisiae genes RHO1 and MRP2. Nucleic Acids Res 1993; 21:5500-8. [PMID: 8265368 PMCID: PMC310593 DOI: 10.1093/nar/21.23.5500] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The Saccharomyces cerevisiae genes RHO1 and MRP2 are convergently transcribed, with 281 base pairs separating their termination codons. Transcript mapping revealed at least 111 base pairs within the RHO1-MRP2 intercoding region are transcribed in both directions. Transplacement experiments showed distinct sequences of 70 nt for MRP2 and 179 nt for RHO1 were sufficient for normal mRNA 3' end formation. The MRP2 signal functioned in either orientation, although relatively inefficiently in the non-native orientation. This element contains a polyAT sequence essential for 3' end formation in both orientations. RHO1 or MRP2 3' end formation was not affected by overproduction or elimination of the complementary, natural antisense transcript. In contrast, insertion of a strong promoter that extended antisense transcripts beyond their normal 3' ends inactivated either MRP2 or RHO1. These data suggest that transcript termination in the compact yeast genome can be important to prevent inactivation of downstream genes as a result of antisense transcription.
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Affiliation(s)
- J A Peterson
- Department of Biochemistry and Biophysics, Iowa State University, Ames 50011
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115
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Huang CY, Yuan CJ, Livanova NB, Graves DJ. Expression, purification, characterization, and deletion mutations of phosphorylase kinase gamma subunit: identification of an inhibitory domain in the gamma subunit. Mol Cell Biochem 1993; 127-128:7-18. [PMID: 7935363 DOI: 10.1007/bf01076753] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A catalytic fragment, gamma 1-298, derived from limited chymotryptic digestion of phosphorylase b kinase (Harris, W.R. et al., J. Biol. Chem., 265: 11740-11745, 1990), is reported to have about six-fold greater specific activity than does the gamma subunit-calmodulin complex. To test whether there is an inhibitory domain located outside the catalytic core of the gamma subunit, full-length wild-type and seven truncated forms of gamma were expressed in E. coli. Recombinant proteins accumulate in the inclusion bodies and can be isolated, solubilized, renatured, and purified further by ammonium sulfate precipitation and Q-Sepharose column. Four out of seven truncated mutants show similar (gamma 1-353 and gamma 1-341) or less (gamma 1-331 and gamma 1-276) specific activity than does the full-length wild-type gamma, gamma 1-386. Three truncated forms, gamma 1-316, gamma 1-300, and gamma 1-290 have molar specific activities approximately twice as great as those of the full-length wild-type gamma and the nonactivated holoenzyme. All recombinant gamma s exhibit similar Km values for both substrates, i.e., about 18 microM for phosphorylase b and about 75 microM for MgATP. Three truncated gamma s, gamma 1-316, gamma 1-300, and gamma 1-290, have a 1.9- to 2.5-fold greater catalytic efficiency (Vmax/Km) than that of the full-length wild-type gamma and a 3.5- to 4.5-fold greater efficiency than that of the truncated gamma 1-331. This evidence suggests that there is at least one inhibitory domain in the C-terminal region of gamma, which is located at gamma 301-331. gamma 1-290, but not gamma 1-276, which contains the highly conserved kinase domain, is the minimum sequence required for the gamma subunit to exhibit phosphotransferase activity. Both gamma 1-290 and gamma 1-300 have several properties similar to full-length wild-type gamma, including metal ion responses (activation by free Mg2+ and inhibition by free Mn2+), pH dependency, and substrate specificities.
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Affiliation(s)
- C Y Huang
- Department of Biochemistry and Biophysics, Iowa State University, Ames 50011
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116
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Chung HH, Benson DR, Cornish VW, Schultz PG. Probing the role of loop 2 in Ras function with unnatural amino acids. Proc Natl Acad Sci U S A 1993; 90:10145-9. [PMID: 8234268 PMCID: PMC47730 DOI: 10.1073/pnas.90.21.10145] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The YDPT sequence motif (residues 32-35) in loop 2 (residues 32-40) of Ha-Ras p21 protein is conserved in the Ras protein family. X-ray crystal structures have revealed significant conformational differences in this region between the GTP- and GDP-bound forms. Moreover, mutations in this region block neoplastic transformation and prevent interaction with GTPase-activating protein (GAP), suggesting that this region may contribute to the effector function of Ras. To better understand the structural features required for GAP interaction and GTPase activity, the expanded repertoire of unnatural amino acid mutagenesis has been used to investigate the roles of the key residues, Pro-34, Thr-35, and Ile-36. A Pro-34-->methanoproline mutant, in which residue 34 is locked in the trans conformation, was found to retain high levels of intrinsic and GAP-activated GTPase activity, making unlikely conformational isomerization at this position. Deletion of a single methyl group from Ile (Ile-36-->norvaline) abolished GAP activation of Ras, revealing a remarkable specificity in this protein-protein interaction. Finally, replacement of Thr-35 with diastereomeric allo-threonine led to inactivation of Ras, demonstrating the importance of the orientation of this critical residue in Ras function.
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Affiliation(s)
- H H Chung
- Department of Chemistry, University of California, Lawrence Berkeley Laboratory, Berkeley 94720-9989
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117
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Heiland S, Knippers R, Kunze N. The promoter region of the human type-I-DNA-topoisomerase gene. Protein-binding sites and sequences involved in transcriptional regulation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 217:813-22. [PMID: 8223637 DOI: 10.1111/j.1432-1033.1993.tb18309.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We examined the promoter of the human type-I-DNA topoisomerase gene (hTOP1) for regions protected against DNase I digestion by nuclear proteins from HeLa or from adenovirus-transformed 293 cells. We identified ten protected DNA sequences within 580 bp of DNA upstream of the transcriptional-start sites and one additional site, which is located between the two clusters of transcriptional-start sites. Several of these protein-binding sites have significant similarities to recognition sequences of known transcription factors including factors Sp1, octamer transcription factor, cAMP-responsive-element-binding protein (CREB/ATF), NF-kappa B and members of the Myc-related family of basic/helix-loop-helix/leucine-zipper proteins. Other protein-binding sites show less or no similarities to known consensus sequences. We investigated the physiological significance of these protein-binding sites using a set of deletion and nucleotide-exchange mutants. We conclude that the expression of the hTOP1 gene is regulated by a complex network of negatively and positively acting transcription factors.
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Affiliation(s)
- S Heiland
- Division of Biology, University of Konstanz, Germany
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118
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Lenz M, Rétey J. Cloning, expression and mutational analysis of the urocanase gene (hutU) from Pseudomonas putida. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 217:429-34. [PMID: 7901006 DOI: 10.1111/j.1432-1033.1993.tb18262.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The histidine-utilizing hutU gene was isolated from a lambda-EMBL3 phage of a genomic library from Pseudomonas putida nicII and subcloned into the expression vector pT7-7. Escherichia coli BL21 cells were transformed with the recombinant plasmid and produced a catalytically active protein, amounting to approximately 30% of the total protein in the crude cell-free extract. The addition of NAD+ to the growth medium ensured the full occupation of active sites by the cofactor. This requires a mechanism for the transport of NAD+ into E. coli cells. Using the overproducing mutant a new, fast and efficient isolation procedure is described which yields electrophoretically homogeneous urocanase within two days. The yield of pure enzyme, based on the culture volume, has been improved 50-80-fold compared with the traditional method. To investigate the possible role of cysteine residues in the catalysis or in the tight binding of the cofactor NAD+, six different mutants were prepared. In each mutant protein, one conserved cysteine was exchanged for alanine. The resulting clones were tested for the expression of urocanase with catalytic activity; the Km and Vmax values were determined. Only Cys410 was essential for catalysis. There was no detectable reconstitution or increase of activity after the addition of NAD+, either in the essential Cys/Ala mutant or the other mutant proteins. Electrospray-mass spectroscopy of the wild-type enzyme revealed that the coenzyme is not covalently bound to the protein and computational analysis showed no typical sequence for a mononucleotide-binding domain like the Rossman fold. To obtain urocanase apoenzyme, P. putida nicII was transformed with pGP1-2 and pTET7-U and grown in nicotinate-depleted medium. Like the mutant proteins, no activation of the apoform occurred after the addition of NAD+. These observations led us to postulate a new model for the non-covalent but tight binding of NAD+ to the enzyme by 'trapping' the cofactor while folding the nascent protein.
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Affiliation(s)
- M Lenz
- Department of Biochemistry, University of Karlsruhe, Germany
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119
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Harrison DA, Gdula DA, Coyne RS, Corces VG. A leucine zipper domain of the suppressor of Hairy-wing protein mediates its repressive effect on enhancer function. Genes Dev 1993; 7:1966-78. [PMID: 7916729 DOI: 10.1101/gad.7.10.1966] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The suppressor of Hairy-wing [su(Hw)] protein mediates the mutagenic effect of the gypsy retrotransposon by repressing the function of transcriptional enhancers controlling the expression of the mutant gene. A structural and functional analysis of su(Hw) was carried out to identify domains of the protein responsible for its negative effect on enhancer action. Sequence comparison among the su(Hw) proteins from three different species allows the identification of evolutionarily conserved domains with possible functional significance. An acidic domain located in the carboxy-terminal end of the Drosophila melanogaster protein is not present in su(Hw) from other species, suggesting a nonessential role for this part of the protein. A second acidic domain located in the amino-terminal region of su(Hw) is present in all species analyzed. This domain is dispensable in the D. melanogaster protein when the carboxy-terminal acidic domain is present, but the protein is nonfunctional when both regions are simultaneously deleted. Mutations in the zinc fingers result in su(Hw) protein unable to interact with DNA in vivo, indicating a functional role for this region of the protein in DNA binding. Finally, a region of su(Hw) homologous to the leucine zipper motif is necessary for the negative effect of this protein on enhancer function, suggesting that su(Hw) might exert this effect by interacting, directly or indirectly, with transcription factors bound to these enhancers.
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Affiliation(s)
- D A Harrison
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
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120
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Regulation of dimorphism in Saccharomyces cerevisiae: involvement of the novel protein kinase homolog Elm1p and protein phosphatase 2A. Mol Cell Biol 1993. [PMID: 8395007 DOI: 10.1128/mcb.13.9.5567] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae genes ELM1, ELM2, and ELM3 were identified on the basis of the phenotype of constitutive cell elongation. Mutations in any of these genes cause a dimorphic transition to a pseudohyphal growth state characterized by formation of expanded, branched chains of elongated cells. Furthermore, elm1, elm2, and elm3 mutations cause cells to grow invasively under the surface of agar medium. S. cerevisiae is known to be a dimorphic organism that grows either as a unicellular yeast or as filamentous cells termed pseudohyphae; although the yeast-like form usually prevails, pseudohyphal growth may occur during conditions of nitrogen starvation. The morphologic and physiological properties caused by elm1, elm2, and elm3 mutations closely mimic pseudohyphal growth occurring in conditions of nitrogen starvation. Therefore, we propose that absence of ELM1, ELM2, or ELM3 function causes constitutive execution of the pseudohyphal differentiation pathway that occurs normally in conditions of nitrogen starvation. Supporting this hypothesis, heterozygosity at the ELM2 or ELM3 locus significantly stimulated the ability to form pseudohyphae in response to nitrogen starvation. ELM1 was isolated and shown to code for a novel protein kinase homolog. Gene dosage experiments also showed that pseudohyphal differentiation in response to nitrogen starvation is dependent on the product of CDC55, a putative B regulatory subunit of protein phosphatase 2A, and a synthetic phenotype was observed in elm1 cdc55 double mutants. Thus, protein phosphorylation is likely to regulate differentiation into the pseudohyphal state.
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121
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Vidal H, Crepin KM, Rider MH, Hue L, Rousseau GG. Cloning and expression of novel isoforms of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from bovine heart. FEBS Lett 1993; 330:329-33. [PMID: 8397106 DOI: 10.1016/0014-5793(93)80898-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Distinct 6-phosphofructo-2-kinase (PFK-2)/fructose 2,6-bisphosphatase (FBPase-2) cDNAs were cloned from bovine heart, showing that PFK-2/FBPase-2 gene B, which contains 16 exons, codes for at least five mRNAs. Three of them (B1, B2, B4) could encode the 58,000-M(r) isozyme. In B2 mRNA, exon 15 encodes four more residues than in B1. In B4 mRNA, exon 15 encodes six more residues than in B1, but exon 16 (20 residues) is missing. B3 mRNA corresponds to the 54,000-M(r) isozyme. It lacks exon 15 and also differs from the other mRNAs in the 5' noncoding region. B5 mRNA encodes a truncated form. When expressed in E. coli, the recombinant isoforms corresponding to all these mRNAs except B5 exhibited PFK-2 activity.
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Affiliation(s)
- H Vidal
- Hormone and Metabolic Research Unit, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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122
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Judice JK, Gamble TR, Murphy EC, de Vos AM, Schultz PG. Probing the mechanism of staphylococcal nuclease with unnatural amino acids: kinetic and structural studies. Science 1993; 261:1578-81. [PMID: 8103944 DOI: 10.1126/science.8103944] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Staphylococcal nuclease is an enzyme with enormous catalytic power, accelerating phosphodiester bond hydrolysis by a factor of 10(16) over the spontaneous rate. The mechanistic basis for this rate acceleration was investigated by substitution of the active site residues Glu43, Arg35, and Arg87 with unnatural amino acid analogs. Two Glu43 mutants, one containing the nitro analog of glutamate and the other containing homoglutamate, retained high catalytic activity at pH 9.9, but were less active than the wild-type enzyme at lower pH values. The x-ray crystal structure of the homoglutamate mutant revealed that the carboxylate side chain of this residue occupies a position and orientation similar to that of Glu43 in the wild-type enzyme. The increase in steric bulk is accommodated by a backbone shift and altered torsion angles. The nitro and the homoglutamate mutants display similar pH versus rate profiles, which differ from that of the wild-type enzyme. Taken together, these studies suggest that Glu43 may not act as a general base, as previously thought, but may play a more complex structural role during catalysis.
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Affiliation(s)
- J K Judice
- Department of Chemistry, University of California, Berkeley 94720
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123
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Meng M, Bagdasarian M, Zeikus JG. The role of active-site aromatic and polar residues in catalysis and substrate discrimination by xylose isomerase. Proc Natl Acad Sci U S A 1993; 90:8459-63. [PMID: 8378319 PMCID: PMC47376 DOI: 10.1073/pnas.90.18.8459] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The functions of individual amino acid residues in the active site of Thermoanaerobacterium thermosulfurigenes D-xylose ketol-isomerase (EC 5.3.1.5) were studied by site-directed substitution. The role of aromatic residues in the active-site pocket was not limited to the creation of a hydrophobic environment. For example, Trp-188 provided for substrate binding and Trp-139 allowed for the discrimination between D-xylose and D-glucose. Substrate discrimination was accomplished by steric hindrance caused by the side chain of Trp-139 toward the larger glucose molecule. Preference of the enzyme for the alpha-anomer of glucose depended on the His-101/Asp-104 pair. Wide differences observed in the catalytic constant (kcat) for alpha- versus beta-glucose in the wild-type enzyme and the fact that only the kcat for alpha-glucose was changed in the His-101-->Asn mutants strongly suggest that the substrate molecule entering the hydride-shift step is still in the cyclic form. On the basis of these results a revised hypothesis for the catalytic mechanism of D-xylose isomerase has been proposed that involves His-101, Asp-104, and Asp-339 functioning as a catalytic triad.
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Affiliation(s)
- M Meng
- Department of Microbiology, Michigan State University, East Lansing 48824
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124
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Zhang ZY, Dixon JE. Active site labeling of the Yersinia protein tyrosine phosphatase: the determination of the pKa of the active site cysteine and the function of the conserved histidine 402. Biochemistry 1993; 32:9340-5. [PMID: 8369304 DOI: 10.1021/bi00087a012] [Citation(s) in RCA: 206] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In this report, we demonstrated that the Yersinia protein tyrosine phosphatase (PTPase) could be inactivated by the alkylating agent iodoacetate. The enzyme modification was selective, and the covalent attachment was stoichiometric. The residue that was labeled by iodoacetate was shown to be Cys403, which was the same catalytically essential residue identified by site-directed mutagenesis [Guan, K. L., & Dixon, J.E. (1990) Science 249, 553-556]. The rate of iodoacetate modification decreased as the ionic strength of the media increased. There was no significant D2O solvent isotope effect associated with the inactivation of the enzyme, suggesting that thiol anion of Cys403 reacted as a nucleophile. The Yersinia PTPase also displayed differential reactivity (940-fold) toward iodoacetate over iodoacetamide. This indicates that residues within the active site of the enzyme are positively charged. The pKa of the active site thiol group was determined to be 4.67. The low pKa value suggests that ionic interactions are important in stabilizing the thiolate anion. One candidate residue for this stabilization is the invariant histidine (His402) found in all PTPases. Substitutions of His402 with Asn or Ala altered the active site thiol pKa to 5.99 and 7.35, respectively. Interestingly, the active site thiol in the mutants also showed enhanced reactivity toward iodoacetate. The second-order rate constants for the inactivation of the wild-type enzyme, H402N, and H402A were 59.7, 3305, and 1763 M-1 min-1, respectively.
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Affiliation(s)
- Z Y Zhang
- Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606
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125
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Baunach G, Maurer B, Hahn H, Kranz M, Rethwilm A. Functional analysis of human foamy virus accessory reading frames. J Virol 1993; 67:5411-8. [PMID: 8394455 PMCID: PMC237942 DOI: 10.1128/jvi.67.9.5411-5418.1993] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Foamy viruses belong to the retroviruses which possess a complex genome structure. The human foamy virus (HFV) isolate bears three open reading frames (the so-called bel genes) in the 3' region of the genome which have been reported to give rise to possibly six different proteins via alternative splicing (W. Muranyi and R. M. Flügel, J. Virol. 65:727-735, 1991). In order to analyze the requirements of these proteins for HFV replication in vitro, we constructed a set of single and combinatory bel gene mutants of an infectious molecular clone of HFV. The mutant which lacked the transacting activator, bel-1, was found to be replication incompetent. All other mutants replicated equally well and gave rise to comparable titers of infectious cell-free virus. When HFV proviruses were put under the control of a heterologous promoter (simian virus 40), none of the accessory gene products was found to be required for expression of structural (gag) proteins. There was no evidence for a posttranscriptional regulatory protein that is present in other complex retroviruses.
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Affiliation(s)
- G Baunach
- Institut für Virologie und Immunbiologie der Universität, Würzburg, Germany
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126
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Lee J, Hwang P, Wilson T. Lysine 319 interacts with both glutamic acid 269 and aspartic acid 240 in the lactose carrier of Escherichia coli. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80687-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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127
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Blacketer MJ, Koehler CM, Coats SG, Myers AM, Madaule P. Regulation of dimorphism in Saccharomyces cerevisiae: involvement of the novel protein kinase homolog Elm1p and protein phosphatase 2A. Mol Cell Biol 1993; 13:5567-81. [PMID: 8395007 PMCID: PMC360278 DOI: 10.1128/mcb.13.9.5567-5581.1993] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The Saccharomyces cerevisiae genes ELM1, ELM2, and ELM3 were identified on the basis of the phenotype of constitutive cell elongation. Mutations in any of these genes cause a dimorphic transition to a pseudohyphal growth state characterized by formation of expanded, branched chains of elongated cells. Furthermore, elm1, elm2, and elm3 mutations cause cells to grow invasively under the surface of agar medium. S. cerevisiae is known to be a dimorphic organism that grows either as a unicellular yeast or as filamentous cells termed pseudohyphae; although the yeast-like form usually prevails, pseudohyphal growth may occur during conditions of nitrogen starvation. The morphologic and physiological properties caused by elm1, elm2, and elm3 mutations closely mimic pseudohyphal growth occurring in conditions of nitrogen starvation. Therefore, we propose that absence of ELM1, ELM2, or ELM3 function causes constitutive execution of the pseudohyphal differentiation pathway that occurs normally in conditions of nitrogen starvation. Supporting this hypothesis, heterozygosity at the ELM2 or ELM3 locus significantly stimulated the ability to form pseudohyphae in response to nitrogen starvation. ELM1 was isolated and shown to code for a novel protein kinase homolog. Gene dosage experiments also showed that pseudohyphal differentiation in response to nitrogen starvation is dependent on the product of CDC55, a putative B regulatory subunit of protein phosphatase 2A, and a synthetic phenotype was observed in elm1 cdc55 double mutants. Thus, protein phosphorylation is likely to regulate differentiation into the pseudohyphal state.
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Affiliation(s)
- M J Blacketer
- Department of Biochemistry and Biophysics, Iowa State University, Ames 50011
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128
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Oliveira CC, van den Heuvel JJ, McCarthy JE. Inhibition of translational initiation in Saccharomyces cerevisiae by secondary structure: the roles of the stability and position of stem-loops in the mRNA leader. Mol Microbiol 1993; 9:521-32. [PMID: 8412699 DOI: 10.1111/j.1365-2958.1993.tb01713.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A new modular gene-expression system for use in studies of translational control in Saccharomyces cerevisiae was constructed. A GAL::PGK fusion promoter (GPF) directed the inducible synthesis of mRNAs initiated at a single major site. A series of leader sequences were tested in combination with each of two reporter genes (encoding chloramphenicol acetyl transferase (cat) and luciferase (luc)). Stem-loop structures of three different sizes and predicted stabilities were inserted into each of two different unique restriction sites in the leader. After correction for relative mRNA abundance, a stem-loop of predicted stability equivalent to approximately -18 kcal mol-1 inhibited translation by up to 89%. The degree of inhibition exerted by the other stem-loops correlated positively with their predicted stabilities. Combinations of two stem-loops at different sites yielded an inhibitory effect greater than that of either individual stem-loop alone. Similar inhibitory effects were observed with both reporter genes. However, inhibition of translation, particularly of the cat gene, was more effective when the stem-loop was positioned close to the start codon rather than at the 5' end of the leader. The observed results reflect an important form of post-transcriptional control that is expected to act on a large number of genes in yeast.
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Affiliation(s)
- C C Oliveira
- Department of Gene Expression, GBF-Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
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129
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Balzarini J, Karlsson A, Vandamme AM, Pérez-Pérez MJ, Zhang H, Vrang L, Oberg B, Bäckbro K, Unge T, San-Félix A. Human immunodeficiency virus type 1 (HIV-1) strains selected for resistance against the HIV-1-specific [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro- 5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)]-beta-D-pentofurano syl (TSAO) nucleoside analogues retain sensitivity to HIV-1-specific nonnucleoside inhibitors. Proc Natl Acad Sci U S A 1993; 90:6952-6. [PMID: 7688467 PMCID: PMC47053 DOI: 10.1073/pnas.90.15.6952] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We recently reported that a newly discovered class of nucleoside analogues--[2',5'-bis-O-(tert-butyldimethylsilyl)- 3'-spiro-5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)]-beta-D - pentofuranosyl derivatives of pyrimidines and purines (designated TSAO)--are highly specific inhibitors of human immunodeficiency virus type 1 (HIV-1) and targeted at the nonsubstrate binding site of HIV-1 reverse transcriptase (RT). We now find that HIV-1 strains selected for resistance against three different TSAO nucleoside derivatives retain sensitivity to the other HIV-1-specific nonnucleoside derivatives (tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), 1-[(2-hydroxyethoxy)methyl]-6-phenylthiothymine, nevirapine, and pyridinone L697,661, as well as to the nucleoside analogues 3'-azido-3'-deoxythymidine, ddI, ddC, and 9-(2-phosphonylmethoxyethyl)adenine. Pol gene nucleotide sequence analysis of the TSAO-resistant and -sensitive HIV-1 strains revealed a single amino acid substitution at position 138 (Glu-->Lys) in the RT of all TSAO-resistant HIV-1 strains. HIV-1 RT in which the Glu-138-->Lys substitution was introduced by site-directed mutagenesis and expressed in Escherichia coli could not be purified because of rapid degradation. However, HIV-1 RT containing the Glu-138-->Arg substitution was stable. It lost its sensitivity to the TSAO nucleosides but not to the other HIV-1-specific RT inhibitors (i.e., TIBO and pyridinone). Our findings point to a specific interaction of the 4''-amino group on the 3'-spiro-substituted ribose moiety of the TSAO nucleosides with the carboxylic acid group of glutamic acid at position 138 of HIV-1 RT.
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Affiliation(s)
- J Balzarini
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Belgium
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130
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Crepin K, Vertommen D, Dom G, Hue L, Rider M. Rat muscle 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Study of the kinase domain by site-directed mutagenesis. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82466-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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131
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132
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Chow CM, RajBhandary UL. Developmental regulation of the gene for formate dehydrogenase in Neurospora crassa. J Bacteriol 1993; 175:3703-9. [PMID: 8509325 PMCID: PMC204785 DOI: 10.1128/jb.175.12.3703-3709.1993] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We have isolated and characterized a gene, fdh, from Neurospora crassa which is developmentally regulated and which produces formate dehydrogenase activity when expressed in Escherichia coli. The gene is closely linked (less than 0.6 kb apart) to the leu-5 gene encoding mitochondrial leucyl-tRNA synthetase; the two genes are transcribed convergently from opposite strands. The expression patterns of these genes differ: fdh mRNA is found only during conidiation and early germination and is not detectable during mycelial growth, while leu-5 mRNA appears during germination and mycelial growth. The structure of the fdh gene was determined from the sequence of cDNA and genomic DNA clones and from mRNA mapping studies. The gene encodes a 375-amino-acid-long protein with sequence similarity to NAD-dependent dehydrogenases of the E. coli 3-phosphoglycerate dehydrogenase (serA gene product) subfamily. In particular, there is striking sequence similarity (52% identity) to formate dehydrogenase from Pseudomonas sp. strain 101. All of the residues thought to interact with NAD in the crystal structure of the Pseudomonas enzyme are conserved in the N. crassa enzyme. We have further shown that expression of the N. crassa gene in E. coli leads to the production of formate dehydrogenase activity, indicating that the N. crassa gene specifies a functional polypeptide.
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Affiliation(s)
- C M Chow
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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133
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Takagi M, Ohta T, Johki S, Imanaka T. Characterization of the membrane sensor PenJ for beta-lactam antibiotics from Bacillus licheniformis by amino acid substitution. FEMS Microbiol Lett 1993; 110:127-31. [PMID: 8319890 DOI: 10.1111/j.1574-6968.1993.tb06306.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The PenJ protein of the penicillinase gene (penP) expression system from Bacillus licheniformis is an antirepressor and membrane receptor for beta-lactam antibiotics. A putative beta-lactam antibiotic binding site including Ser402 and Lys405, which are homologous to the conserved sequence for the beta-lactam binding site (Ser-X-X-Lys) is present. An amino acid substitution was introduced at Ser402 to Ala, removing the hydroxyl group of the serine. The mutant PenJ, S402A, was still functional. However, two other mutants, S402T (Ser402-->Thr) and K405A (Lys405-->Ala), were not functional. Thus, the hydroxyl group of Ser402 does not appear to be important for penicillin binding. Amino acid substitutions (K539R, D591N and K539R.G541V) were introduced in PenJ in the region of the putative phosphoryl binding domain. None of these mutant PenJ proteins was a functional antirepressor. These results suggested that the putative phosphoryl binding domain might be an important region for signal transduction.
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Affiliation(s)
- M Takagi
- Department of Biotechnology, Faculty of Engineering, Osaka University, Japan
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134
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Lloubès R, Lazdunski C, Granger-Schnarr M, Schnarr M. DNA sequence determinants of LexA-induced DNA bending. Nucleic Acids Res 1993; 21:2363-7. [PMID: 8506133 PMCID: PMC309533 DOI: 10.1093/nar/21.10.2363] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The LexA repressor from Escherichia coli induces DNA bending upon interaction with the two overlapping operators which regulate the transcription of the colicin A encoding gene caa. Both caa operators harbor T-tracts adjacent to their recognition motifs. These tracts have been suggested to be especially favorable for the promotion of LexA-induced DNA bending. Here we show that this is indeed the case, since disruption of the TTTT-tract adjacent to operator O1 by the replacement of the two central thymine bases by AA, GA or CG markedly reduces LexA-induced DNA bending. Simple A.T-richness in this position is thus not sufficient to promote full LexA-induced bending, albeit a TAAT sequence is always more efficient to promote bending than those sequences containing one or two C/G base pairs.
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Affiliation(s)
- R Lloubès
- Centre de Biochimie et de Biologie Moléculaire, Marseille, France
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135
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Communi D, Takazawa K, Erneux C. Lys-197 and Asp-414 are critical residues for binding of ATP/Mg2+ by rat brain inositol 1,4,5-trisphosphate 3-kinase. Biochem J 1993; 291 ( Pt 3):811-6. [PMID: 8387779 PMCID: PMC1132441 DOI: 10.1042/bj2910811] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Rat brain inositol 1,4,5-trisphosphate (InsP3) 3-kinase A was expressed in Escherichia coli in order to identify the amino acid residues involved in substrate ATP/Mg2+ binding. Two amino acid regions that are conserved in the catalytic domain of InsP3 3-kinase isoenzymes A and B had characteristics consistent with two ATP/Mg(2+)-binding motives. Site-directed mutagenesis was performed on residues Lys-197, Lys-207 and Asp-414 to generate three mutant enzymes, referred to as C5 K197I, C5 K207I and C5 D414N. Comparison of the wild-type and mutant proteins with regard to enzymic activity revealed that C5 K197I exhibited 10% of control enzyme activity, C5 D414N was totally inactive and C5 K207I was fully active. The reduced levels of enzyme activity for C5 K197I and C5 D414N were correlated with an altered ability of the mutant enzymes to bind ATP/Mg2+, as determined by ATP-agarose affinity chromatography. Neither Ca2+/calmodulin binding nor InsP3 binding appeared to be affected. Mutant C5 K207I showed the same characteristics as the wild-type enzyme. Taken together, these results strongly indicated (i) that amino acid residues Lys-197 and Asp-414 are necessary for InsP3 3-kinase activity and form part of the ATP/Mg(2+)-binding domain, and (ii) that amino acid residues Lys-197, Lys-207 and Asp-414 are not involved in either InsP3 binding or enzyme stimulation by Ca2+/calmodulin.
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Affiliation(s)
- D Communi
- Institut de Recherche Interdisciplinaire (IRIBHN), Université Libre de Bruxelles, Belgium
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136
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Felsenstein KM, Lewis-Higgins L. Processing of the beta-amyloid precursor protein carrying the familial, Dutch-type, and a novel recombinant C-terminal mutation. Neurosci Lett 1993; 152:185-9. [PMID: 8515875 DOI: 10.1016/0304-3940(93)90514-l] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mutations within the beta-amyloid precursor protein (beta-APP) gene that cosegregate with early onset familial Alzheimer's disease (FAD) and hereditary cerebral hemorrhage with amyloidosis of the Dutch-type (HCHWA-D) have been reported. The effects of these mutations on the products of both the non-amyloidogenic and potentially amyloidogenic processing pathways of the beta-APP protein were examined in stably transfected cells. Processing of these mutants appeared to be the same as wild-type. These results contrasted sharply to those observed with a mutation near the amino terminus of the beta-protein domain of beta-APP. This mutation resulted in a two-fold decrease of a potentially amyloidogenic 11 kDa peptide fragment. The data suggest that the FAD and HCHWA-D mutations have no effect on the formation of potentially amyloidogenic fragments in this cell system, possibly implicating an alternative mechanism for their effects.
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Affiliation(s)
- K M Felsenstein
- CNS-Department of Biophysics and Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, CT 06492
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137
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Yoshimura FK, Diem K, Chen H, Tupper J. A protein-binding site with dyad symmetry in the long terminal repeat of the MCF13 murine leukemia virus that contributes to transcriptional activity in T lymphocytes. J Virol 1993; 67:2298-304. [PMID: 8383242 PMCID: PMC240375 DOI: 10.1128/jvi.67.4.2298-2304.1993] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We have previously identified regions in the long terminal repeat (LTR) of the MCF13 murine leukemia virus (MLV) that contribute to transcriptional activity in different cell types. We have observed that enhancer sequences and a region that resides 3' of the enhancer make significant contributions to transcriptional activity in T lymphocytes (T. Hollon and F. K. Yoshimura, J. Virol. 63:3353-3361, 1989). In this report, we have focused on the region of the MCF13 LTR that is 3' of the enhancer to identify binding sites for proteins that may play a role in the regulation of transcription in T cells. By gel shift and DNA footprint analyses, we have identified a single protein-binding site (MLPal) that includes a nucleotide sequence with dyad symmetry. A synthetic double-stranded oligonucleotide corresponding to this protein-binding site formed a specific protein-DNA complex. Deletion of this protein-binding site from the wild-type LTR decreased transcriptional activity in T lymphocytes but not in fibroblasts as determined by a transient expression assay. The MLPal sequence by itself cannot augment transcription in T cells but is able to do so in conjunction with enhancer sequences.
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Affiliation(s)
- F K Yoshimura
- Department of Biological Structure, University of Washington, Seattle 98195
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138
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Bech LM, Sørensen SB, Breddam K. Significance of hydrophobic S4-P4 interactions in subtilisin 309 from Bacillus lentus. Biochemistry 1993; 32:2845-52. [PMID: 8457550 DOI: 10.1021/bi00062a016] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The subtilisins have an extended substrate binding cleft comprising at least 8 subsites. Two pockets at the S1 and S4 sites are particularly conspicuous, and the interactions between substrate and these two pockets are very important for the substrate specificity. Phe residues have mutationally been introduced at one of positions 102, 128, 130, and 132 of the subtilisin Savinase from Bacillus lentus to investigate the effects of introducing bulky groups along the rim of the S4 binding pocket. It is shown that the marked P4 preference of wild-type Savinase for aromatic groups is eliminated by the Gly102-->Phe and Ser128-->Phe mutations, indicating that bulky groups at positions 102 and 128 block the S4 binding site. In contrast, the activity toward hydrophilic P4 residues is not nearly as affected by these mutations, suggesting that the binding mode of the P4 side chain is dependent on its properties. Introduction of a bulky -CH2-S-CH2-CH2-pyridyl group at position 128, by mutational incorporation of Cys followed by chemical modification with 2-vinylpyridine, has essentially the same effect. The Ser130-->Phe mutation hardly affects the activity of the enzyme while the Ser-->Phe mutation at position 132 renders the preference for hydrophobic groups in P4 even more pronounced. This mutation furthermore affects the size of the S4 pocket. An analysis of double mutants at positions 132 and 104 suggests that the S4 region is flexible and is adjusted upon binding of substrates.
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Affiliation(s)
- L M Bech
- Department of Chemistry, Carlsberg Laboratory, Copenhagen Valby, Denmark
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139
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Stüber D, Friedlein A, Fountoulakis M, Lahm HW, Garotta G. Alignment of disulfide bonds of the extracellular domain of the interferon gamma receptor and investigation of their role in biological activity. Biochemistry 1993; 32:2423-30. [PMID: 8443182 DOI: 10.1021/bi00060a038] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The extracellular ligand binding domain of the human interferon gamma receptor includes eight cysteine residues forming four disulfide bonds. Only the nonreduced protein binds interferon gamma. We investigated the alignment of the disulfide bonds, using an enzymatically deglycosylated form of a soluble interferon gamma receptor, produced in baculovirus-infected insect cells. The soluble receptor was digested with endoproteinase Glu-C and proteinase K, and the proteolytic fragments were characterized by amino acid sequence analysis and mass spectrometry. It was found that four consecutive disulfide bonds are formed between residues Cys60-Cys68, Cys105-Cys150, Cys178-Cys183, and Cys197-Cys218. We also investigated the role of the disulfide bonds in biological activity of the receptor, using site-directed mutagenesis and by exchanging the cysteine residues for serines. The mutated proteins were expressed in Escherichia coli and analyzed for ligand binding capacity on protein blots. The assays showed that all disulfide bonds are essential for full ligand binding capacity. Double or quadruple mutations at cysteine residues 60 and 68, and residues 178, 183, 197, and 218, respectively, resulted in complete loss of the activity, whereas double mutations at residues 105 and 150, 178 and 183, and 197 and 218, respectively, resulted in a residual activity about 1 order of magnitude lower than that of the wild type. The specific antibodies gamma R38 and gamma R99 detected conformational epitopes stabilized by disulfide bonds involving cysteine residues 60 and 68, and 178 and 183, respectively.
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Affiliation(s)
- D Stüber
- Department of Biology, Pharmaceutical Research-New Technologies, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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140
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Someya Y, Inagaki N, Maekawa T, Seino Y, Ishii S. Two 3',5'-cyclic-adenosine monophosphate response elements in the promoter region of the human gastric inhibitory polypeptide gene. FEBS Lett 1993; 317:67-73. [PMID: 8428636 DOI: 10.1016/0014-5793(93)81493-j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Transfection of chimeric chloramphenicol acetyltransferase plasmids containing various deletions of the human gastric inhibitory polypeptide (GIP) promoter into hamster insulinoma (HIT T15) cells indicated that the region between -180 and +14 is sufficient for basal promoter activity. Two CRE-BP1 binding sites were identified in this promoter region by DNase I footprinting with the bacterially expressed cAMP response element (CRE) binding protein, CRE-BP1. Mutation analyses showed that these two CREs are required for the basal promoter activity, and furthermore that one site, at nucleotide-158, contributed mainly to the cAMP inducibility of the GIP promoter in HIT T15 cells. Interestingly, the GIP promoter activity was repressed by the c-jun proto-oncogene product, possibly through the CREs.
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Affiliation(s)
- Y Someya
- Department of Medicine, Kyoto University School of Medicine, Japan
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141
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Meinnel T, Guillon JM, Mechulam Y, Blanquet S. The Escherichia coli fmt gene, encoding methionyl-tRNA(fMet) formyltransferase, escapes metabolic control. J Bacteriol 1993; 175:993-1000. [PMID: 8432722 PMCID: PMC193011 DOI: 10.1128/jb.175.4.993-1000.1993] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The genetic organization near the recently cloned fmt gene, encoding Escherichia coli methionyl-tRNA(fMet) formyltransferase (J. M. Guillon, Y. Mechulam, J. M. Schmitter, S. Blanquet, and G. Fayat, J. Bacteriol. 174:4294-4301, 1992), has been studied. The fmt gene, which starts at a GUG codon, is cotranscribed with another gene, fms, and the transcription start site of this operon has been precisely mapped. Moreover, the nucleotide sequence of a 1,379-bp fragment upstream from fmt reveals two additional open reading frames, in the opposite polarity. In the range of 0.3 to 2 doublings per h, the intracellular methionyl-tRNA(fMet) formyltransferase concentration remains constant, providing, to our knowledge, the first example of a gene component of the protein synthesis apparatus escaping metabolic control. When the gene fusion technique was used for probing, no effect on fmt expression of the concentrations of methionyl-tRNA(fMet) formyltransferase or tRNA(fMet) could be found. The possibility that the fmt gene, the product of which is present in excess to ensure full N acylation of methionyl-tRNA(fMet), could be expressed in a constitutive manner is discussed.
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Affiliation(s)
- T Meinnel
- Laboratoire de Biochimie, Centre National de la Recherche Scientifique, Palaiseau, France
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142
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Lohmer S, Maddaloni M, Motto M, Salamini F, Thompson RD. Translation of the mRNA of the maize transcriptional activator Opaque-2 is inhibited by upstream open reading frames present in the leader sequence. THE PLANT CELL 1993; 5:65-73. [PMID: 8439744 PMCID: PMC160251 DOI: 10.1105/tpc.5.1.65] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The protein encoded by the Opaque-2 (O2) gene is a transcription factor, translated from an mRNA that possesses an unusually long 5' leader sequence containing three upstream open reading frames (uORFs). The efficiency of translation of O2 mRNA has been tested in vivo by a transient assay in which the level of activation of the b32 promoter, a natural target of O2 protein, is measured. We show that uORF-less O2 alleles possess a higher transactivation value than the wild-type allele and that the reduction in transactivation due to the uORFs is a cis-dominant effect. The data presented indicate that both uORF1 and uORF2 are involved in the reducing effect and suggest that both are likely to be translated.
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Affiliation(s)
- S Lohmer
- Max-Planck-Institut für Züchtungsforschung, Köln, Germany
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143
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Point mutagenesis of carboxyl-terminal amino acids of cholesteryl ester transfer protein. Opposite faces of an amphipathic helix important for cholesteryl ester transfer or for binding neutralizing antibody. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53947-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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144
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Guarnieri F, Arterburn L, Penno M, Cha Y, August J. The motif Tyr-X-X-hydrophobic residue mediates lysosomal membrane targeting of lysosome-associated membrane protein 1. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53945-4] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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145
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Kulpa J, Dixon J, Pan G, Sadowski P. Mutations of the FLP recombinase gene that cause a deficiency in DNA bending and strand cleavage. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)54047-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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146
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Site-specific immobilization of an L-lactate dehydrogenase via an engineered surface cysteine residue. Biotechnol Lett 1993. [DOI: 10.1007/bf00131548] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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147
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Olsen DB, Sayers JR, Eckstein F. Site-directed mutagenesis of single-stranded and double-stranded DNA by phosphorothioate approach. Methods Enzymol 1993; 217:189-217. [PMID: 8386289 DOI: 10.1016/0076-6879(93)17063-b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- D B Olsen
- Merck Sharp and Dohme, Research Laboratories, West Point, Pennsylvania 19486
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148
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A functional analysis of the genes Enhancer of split and HLH-m5 during early neurogenesis in Drosophila melanogaster. ACTA ACUST UNITED AC 1993; 203:10-17. [DOI: 10.1007/bf00539885] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/1993] [Accepted: 04/19/1993] [Indexed: 10/26/2022]
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149
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Ohyama K, Yamano Y, Chaki S, Kondo T, Inagami T. Domains for G-protein coupling in angiotensin II receptor type I: studies by site-directed mutagenesis. Biochem Biophys Res Commun 1992; 189:677-83. [PMID: 1472039 DOI: 10.1016/0006-291x(92)92254-u] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To delineate domains essential for G-protein coupling in angiotensin II type 1 receptor (AT1), we mutated the receptor cDNA in the putative cytosolic regions and determined consequent changes in the effect of GTP analogs on angiotensin II (Ang II) binding and in inositol trisphosphate production in response to Ang II. Polar residues in targeted areas were replaced by small neutral residues. Mutations in the second cytosolic loop, carboxy terminal region of the third cytosolic loop or deletional mutation in the carboxyl terminal tail simultaneously abolished both the GTP-induced shift to the low affinity form and Ang II-induced stimulation of inositol trisphosphate production. These results suggest that polar residues in the second cytosolic loop, the carboxy terminal region of the third cytosolic loop, and the carboxy terminal cytosolic tail are important for G-protein coupling of AT1 receptor.
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Affiliation(s)
- K Ohyama
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232
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150
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Tupper JC, Chen H, Hays EF, Bristol GC, Yoshimura FK. Contributions to transcriptional activity and to viral leukemogenicity made by sequences within and downstream of the MCF13 murine leukemia virus enhancer. J Virol 1992; 66:7080-8. [PMID: 1331510 PMCID: PMC240380 DOI: 10.1128/jvi.66.12.7080-7088.1992] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have identified nucleotide sequences that regulate transcription in both a cell-type-specific and general manner in the long terminal repeat of the MCF13 murine leukemia virus. Besides the enhancer element, we have observed that the region between the enhancer and promoter (DEN) has a profound effect on transcription in different cell types. This effect, however, was dependent on the copy number of enhancer repeats and was detectable in the presence of a single repeat. When two enhancer repeats were present, the effect of DEN on transcription was abrogated except in T cells. DEN also makes a significant contribution to the leukemogenic property of the MCF13 retrovirus. Its deletion from the MCF13 virus dramatically reduced the incidence of thymic lymphoma and increased the latency of disease in comparison with the wild-type virus. This effect was most marked when one rather than two enhancer repeats was present in the mutant viruses. We also observed that the removal of one repeat alone remarkably reduced leukemogenicity by the MCF13 virus. A newly identified protein-binding site (MLPal) located within DEN affects transcription only in T cells, and its deletion attenuates the ability of an MCF13 virus with a single enhancer repeat to induce thymic lymphoma. This observation suggests that the MLPal protein-binding site contributes to the effect of the DEN region on T-cell-specific transcription and viral leukemogenicity. This study identifies the importance of nonenhancer sequences in the long terminal repeat for the oncogenesis of the MCF13 retrovirus.
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MESH Headings
- 3T3 Cells
- Animals
- Animals, Newborn
- Base Sequence
- Binding Sites
- Cell Line
- Chloramphenicol O-Acetyltransferase/genetics
- Chloramphenicol O-Acetyltransferase/metabolism
- DNA, Viral/genetics
- DNA-Binding Proteins/metabolism
- Enhancer Elements, Genetic
- Leukemia Virus, Murine/genetics
- Leukemia Virus, Murine/pathogenicity
- Leukemia, Experimental/microbiology
- Lymphoma/microbiology
- Mice
- Mice, Inbred AKR
- Molecular Sequence Data
- Muridae
- Mutagenesis, Site-Directed
- Oligodeoxyribonucleotides
- Recombinant Proteins/metabolism
- Repetitive Sequences, Nucleic Acid
- Restriction Mapping
- Sequence Deletion
- Thymus Neoplasms/microbiology
- Transcription, Genetic
- Transfection
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Affiliation(s)
- J C Tupper
- Department of Biological Structure, University of Washington, Seattle 98195
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