151
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Moscufo N, Chow M. Myristate-protein interactions in poliovirus: interactions of VP4 threonine 28 contribute to the structural conformation of assembly intermediates and the stability of assembled virions. J Virol 1992; 66:6849-57. [PMID: 1331497 PMCID: PMC240287 DOI: 10.1128/jvi.66.12.6849-6857.1992] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The VP4 capsid protein of poliovirus is N-terminally modified with myristic acid. Within the poliovirus structure, a hydrogen bond is observed between the myristate carbonyl and the hydroxyl side chain of threonine 28 of VP4. This interaction is between two fivefold symmetry-related copies of VP4 and is one of several myristoyl-mediated interactions that appears to structurally link the promoters within the pentamer subunit of the virus particle. Site-specific substitutions of the threonine residue were constructed to investigate the biological relevance of these myristate-protein interactions. Replacement of the threonine with glycine or lysine is lethal, generating nonviable viruses. Substitution with serine or valine led to viable viruses, but these mutants displayed anomalies during virus assembly. In addition, both assembled serine- and valine-substituted virion particles showed reduced infectivity and were more sensitive to thermal inactivation and antibody neutralization. Thus the threonine residue provides interactions necessary for efficient assembly of the virus and for virion stability.
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Affiliation(s)
- N Moscufo
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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152
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The regulation of the human tumor necrosis factor alpha promoter region in macrophage, T cell, and B cell lines. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41641-9] [Citation(s) in RCA: 150] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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153
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Bech LM, Sørensen SB, Breddam K. Mutational replacements in subtilisin 309. Val104 has a modulating effect on the P4 substrate preference. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:869-74. [PMID: 1425695 DOI: 10.1111/j.1432-1033.1992.tb17359.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The previous notion that the amino acid side chain at position 104 of subtilisins is involved in the binding of the side chain at position P4 of the substrate has been investigated. The amino acid residue Val104 in subtilisin 309 has been replaced by Ala, Arg, Asp, Phe, Ser, Trp and Tyr by site-directed mutagenesis. It is shown that the P4 specificity of this enzyme is not determined solely by the amino acid residue occupying position 104, as the enzyme exhibits a marked preference for aromatic groups in P4, regardless of the nature of the position-104 residue. With hydrophilic amino acid residues at this position, no involvement is seen in binding of either hydrophobic or hydrophilic amino acid residues at position P4 of the substrates. The substrate with Asp in P4 is an exception, as the preference for this substrate is increased dramatically by introduction of an arginine residue at position 104 in the enzyme, presumably due to a substrate-induced conformational change. However, when position 104 is occupied by hydrophobic residues, it is highly involved in binding of hydrophobic amino acid residues, either by increasing the hydrophobicity of S4 or by determining the size of the pocket. The results suggest that the amino acid residue at position 104 is mobile such that it is positioned in the S4 binding site only when it can interact favourably with the substrate's side chain at position P4.
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Affiliation(s)
- L M Bech
- Carlsberg Laboratory, Department of Chemistry, Copenhagen Valby, Denmark
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154
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Nishimura C, Ekida T, Nomura K, Sakamoto K, Suzuki H, Yasukawa K, Kishimoto T, Arata Y. Role of leucine residues in the C-terminal region of human interleukin-6 in the biological activity. FEBS Lett 1992; 311:271-5. [PMID: 1327882 DOI: 10.1016/0014-5793(92)81118-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Site-directed mutagenesis of two sets of three periodic leucine residues which appear at every seventh position in the C-terminal region of human interleukin-6 (IL-6) was performed. Both receptor-binding and immunoglobulin (Ig)-induction activities of a triple mutant Leu168,175,182-->Val were only 1% compared with those of wild-type IL-6. However, the mutant Leu152,159,166-->Val had 13% receptor-binding and 2% Ig-induction activities of those of wild-type IL-6. In order to obtain more direct information on the receptor-binding region, we prepared two synthetic peptides. A significant binding activity was observed for the peptide Leu168-Met185, but not for the peptide Leu152-Arg169. These results indicate that leucine residues in the C-terminal region, especially Leu168, Leu175, and Leu182, play an important role in the receptor-binding and Ig-induction activities.
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Affiliation(s)
- C Nishimura
- Faculty of Pharmaceutical Sciences, University of Tokyo, Japan
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155
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Hirata R, Anraku Y. Mutations at the putative junction sites of the yeast VMA1 protein, the catalytic subunit of the vacuolar membrane H(+)-ATPase, inhibit its processing by protein splicing. Biochem Biophys Res Commun 1992; 188:40-7. [PMID: 1417861 DOI: 10.1016/0006-291x(92)92347-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A single gene, VMA1, encodes the 69-kDa subunit of the vacuolar membrane H(+)-ATPase in the yeast Saccharomyces cerevisiae. We have proposed that the subunit is synthesized as a precursor of 120 kDa (1,071 amino acids) and then converted to the 69-kDa form by an unusual processing reaction, which removes the internal domain of 454 amino acids (residues 284-737) and joins the N- and C-terminal domains. Cysteine to serine mutations at residues 284 and 738, the residues that bracket the internal domain, were introduced into the VMA1 gene by site-directed mutagenesis, and the mutant genes were expressed in a null vma1 mutant. Cells harboring either of the mutant vma1 genes accumulate nonfunctional fragments of the subunit. The mutation of Cys-284 inhibited the cleavage of the N-terminal junction site. Cys-738-->Ser mutation appeared to block the processing at both junction sites although the mutant gene yielded a small fraction of the functional 69-kDa subunit.
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Affiliation(s)
- R Hirata
- Department of Biology, Faculty of Science, University of Tokyo, Japan
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156
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Lee J, Hwang P, Hansen C, Wilson T. Possible salt bridges between transmembrane alpha-helices of the lactose carrier of Escherichia coli. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36751-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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157
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Tomasz J, Shaw BR, Porter K, Spielvogel BF, Sood A. Das 5′-P-boransubstituierte Thymidinphosphat und -triphosphat. Angew Chem Int Ed Engl 1992. [DOI: 10.1002/ange.19921041030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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158
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Crepin K, De Cloedt M, Vertommen D, Foret D, Michel A, Rider M, Rousseau G, Hue L. Molecular forms of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase expressed in rat skeletal muscle. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36668-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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159
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DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae. Mol Cell Biol 1992. [PMID: 1508200 DOI: 10.1128/mcb.12.9.4026] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A mutant of Saccharomyces cerevisiae defective in the S-adenosylmethionine (AdoMet)-dependent methyltransferase step of diphthamide biosynthesis was selected by intracellular expression of the F2 fragment of diphtheria toxin (DT) and shown to belong to complementation group DPH5. The DPH5 gene was cloned, sequenced, and found to encode a 300-residue protein with sequence similarity to bacterial AdoMet:uroporphyrinogen III methyltransferases, enzymes involved in cobalamin (vitamin B12) biosynthesis. Both DPH5 and AdoMet:uroporphyrinogen III methyltransferases lack sequence motifs commonly found in other methyltransferases and may represent a new family of AdoMet:methyltransferases. The DPH5 protein was produced in Escherichia coli and shown to be active in methylation of elongation factor 2 partially purified from the dph5 mutant. A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival. The dph5 null mutant survived expression of three enzymically attenuated DT fragments but was killed by expression of fully active DT fragment A. Consistent with these results, elongation factor 2 from the dph5 null mutant was found to have weak ADP-ribosyl acceptor activity, which was detectable only in the presence of high concentrations of fragment A.
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160
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Serrano L, Sancho J, Hirshberg M, Fersht AR. Alpha-helix stability in proteins. I. Empirical correlations concerning substitution of side-chains at the N and C-caps and the replacement of alanine by glycine or serine at solvent-exposed surfaces. J Mol Biol 1992; 227:544-59. [PMID: 1404368 DOI: 10.1016/0022-2836(92)90906-z] [Citation(s) in RCA: 179] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The importance of amino acid side-chains in helix stability has been investigated by making a series of mutations at the N-caps, C-caps and internal positions of the solvent-exposed faces of the two alpha-helices of barnase. There is a strong positional and context dependence of the effect of a particular amino acid on stability. Correlations have been found that provide insight into the physical basis of helix stabilization. The relative effects of Ala and Gly (or Ser) may be rationalized on the basis of solvent-accessible surface areas: burial of hydrophobic surface stabilizes the protein as does exposure to solvent of unpaired hydrogen bond donors or acceptors in the protein. There is a good correlation between the relative stabilizing effects of Ala and Gly at internal positions with the total change in solvent-accessible hydrophobic surface area of the folded protein on mutation of Ala----Gly. The relationship may be extended to the N and C-caps by including an extra term in hydrophilic surface area for the solvent exposure of the non-intramolecularly hydrogen-bonded main-chain CO, NH or protein side-chain hydrogen bonding groups. The requirement for solvent exposure of the C-cap main-chain CO groups may account for the strong preference for residues having positive phi and psi angles at this position, since this alpha L-conformation results in the largest solvent exposure of the C-terminal CO groups. Glycine in an alpha L-conformation results in the greatest exposure of these CO groups. Further, the side-chains of His, Asn, Arg and Lys may, with positive phi and psi-angles, form a hydrogen bond with the backbone CO of residue in position C -3 (residues are numbered relative to the C-cap). The preferences at the C-cap are Gly much greater than His greater than Asn greater than Arg greater than Lys greater than Ala approximately Ser approximately greater than Asp. The preferences at the N-cap are determined by hydrogen bonding of side-chains or solvent to the exposed backbone NH groups and are: Thr approximately Asp approximately Ser greater than Gly approximately Asn greater than Gln approximately Glu approximately His greater than Ala greater than Val much greater than Pro. These general trends may be obscured when mutation allows another side-chain to become a surrogate cap.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- L Serrano
- MRC Unit for Protein Function and Design Cambridge Centre for Protein Engineering, U.K
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161
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Horovitz A, Matthews JM, Fersht AR. Alpha-helix stability in proteins. II. Factors that influence stability at an internal position. J Mol Biol 1992; 227:560-8. [PMID: 1404369 DOI: 10.1016/0022-2836(92)90907-2] [Citation(s) in RCA: 200] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The solvent-exposed residue Ala32 in the second alpha-helix of barnase was replaced by all other naturally occurring amino acids and the concomitant effects on the protein stability were determined. The results are assumed to reflect both the distinct conformational preferences of the different amino acids and also possible intrahelical interactions. The conformational preferences may be fully rationalized by invoking only a few physical principles. The results agree well with recently experimentally determined rank-order of helix-forming tendencies determined on a model peptide. There is very weak correlation between the results and the experimental host-guest values. There is a weak correlation between our results and the statistical helix propensities and a slightly better correlation with the positional-dependent statistical parameters of J. S. Richardson, and D. C. Richardson.
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Affiliation(s)
- A Horovitz
- Cambridge Centre for Protein Engineering, Department of Chemistry, University of Cambridge, U.K
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162
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Wehner A, Harms E, Jennings MP, Beacham IR, Derst C, Bast P, Röhm KH. Site-specific mutagenesis of Escherichia coli asparaginase II. None of the three histidine residues is required for catalysis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 208:475-80. [PMID: 1521538 DOI: 10.1111/j.1432-1033.1992.tb17210.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Site-specific mutagenesis was used to replace the three histidine residues of Escherichia coli asparaginase II (EcA2) with other amino acids. The following enzyme variants were studied: [H87A]EcA2, [H87L]EcA2, [H87K]EcA2, [H183L]EcA2 and [H197L]EcA2. None of the mutations substantially affected the Km for L-aspartic acid beta-hydroxamate or impaired aspartate binding. The relative activities towards L-Asn, L-Gln, and l-aspartic acid beta-hydroxamate were reduced to the same extent, with residual activities exceeding 10% of the wild-type values. These data do not support a number of previous reports suggesting that histidine residues are essential for catalysis. Spectroscopic characterization of the modified enzymes allowed the unequivocal assignment of the histidine resonances in 1H-NMR spectra of asparaginase II. A histidine signal previously shown to disappear upon aspartate binding is due to His183, not to the highly conserved His87. The fact that [H183L]EcA2 has normal activity but greatly reduced stability in the presence of urea suggests that His183 is important for the stabilization of the native asparaginase tetramer. 1H-NMR and fluorescence spectroscopy indicate that His87 is located in the interior of the protein, possibly adjacent to the active site.
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Affiliation(s)
- A Wehner
- Institut für Physiologische Chemie, Philipps-Universität, Marburg, Federal Republic of Germany
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163
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Møller LB, Ploug M, Blasi F. Structural requirements for glycosyl-phosphatidylinositol-anchor attachment in the cellular receptor for urokinase plasminogen activator. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 208:493-500. [PMID: 1325912 DOI: 10.1111/j.1432-1033.1992.tb17213.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The urokinase-plasminogen-activator receptor (u-PAR) is a glycosyl-phosphatidylinositol(glycosyl-PtdIns)-anchored membrane protein. Using site-directed mutagenesis, we have studied features in the u-PAR sequence important for successful glycosyl-PtdIns attachment. Two critical sequence elements were identified. In the sequence Ser282-Gly283-Ala284, simultaneous substitution of all of these residues prevented membrane anchoring. Individual substitution of each of the residues indicated that Gly283 is the more critical residue and the likely attachment site. However, it was unexpectedly found that mutation of this residue gave rise only to a partial impairment of glycosyl-PtdIns attachment. We therefore propose that more than one residue within this sequence can be utilized as glycosyl-PtdIns-attachment site. In the last eight COOH-terminal amino acids encoded in u-PAR cDNA, deletion of this sequence (residues 306-313) completely prevented glycosyl-PtdIns attachment. However, the remaining COOH-terminal region proved still to possess a potential glycosyl-PtdIns signal activity; it could be converted to a new functional glycosyl-PtdIns signal by substitution of a single positively charged residue (Arg304). Substitution of Arg304 by Leu converted this truntaced u-PAR to a glycosyl-PtdIns-anchored protein, indistinguishable from the wild type. Substitution of Arg304 by a negatively charged residue (Glu) led to a partial acquisition of the glycosyl-PtdIns-anchoring ability. These findings show that charged amino acids placed in the COOH-terminus interfere negatively with glycosyl-PtdIns-anchoring, and, furthermore, that this effect is more pronounced for positively charged than for negatively charged amino acid residues.
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Affiliation(s)
- L B Møller
- Institute of Microbiology, University of Copenhagen, Denmark
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164
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Mattheakis LC, Shen WH, Collier RJ. DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae. Mol Cell Biol 1992; 12:4026-37. [PMID: 1508200 PMCID: PMC360293 DOI: 10.1128/mcb.12.9.4026-4037.1992] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A mutant of Saccharomyces cerevisiae defective in the S-adenosylmethionine (AdoMet)-dependent methyltransferase step of diphthamide biosynthesis was selected by intracellular expression of the F2 fragment of diphtheria toxin (DT) and shown to belong to complementation group DPH5. The DPH5 gene was cloned, sequenced, and found to encode a 300-residue protein with sequence similarity to bacterial AdoMet:uroporphyrinogen III methyltransferases, enzymes involved in cobalamin (vitamin B12) biosynthesis. Both DPH5 and AdoMet:uroporphyrinogen III methyltransferases lack sequence motifs commonly found in other methyltransferases and may represent a new family of AdoMet:methyltransferases. The DPH5 protein was produced in Escherichia coli and shown to be active in methylation of elongation factor 2 partially purified from the dph5 mutant. A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival. The dph5 null mutant survived expression of three enzymically attenuated DT fragments but was killed by expression of fully active DT fragment A. Consistent with these results, elongation factor 2 from the dph5 null mutant was found to have weak ADP-ribosyl acceptor activity, which was detectable only in the presence of high concentrations of fragment A.
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Affiliation(s)
- L C Mattheakis
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
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165
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Medynski D. Genetic Approaches to Protein Structure and Function: Point Mutations as Modifiers of Protein Function. Nat Biotechnol 1992; 10:1002-6. [PMID: 1368997 DOI: 10.1038/nbt0992-1002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this review, I summarize data in the biological literature which underscore the utility of a genetic approach to protein structure/function problems, with emphasis on binding phenomena, particularly of cytokine and growth factor/receptor interactions. Useful parallels or contrasts to chemical ligand/receptor systems and DNA binding protein interactions are examined where they simplify the analysis of protein ligand/receptor interactions. This approach was prompted by the fact that purely rational approaches, based on resolution of the three dimensional structure of proteins, are limited because such data is available for fewer than 3% of the 17,000 proteins for which the amino acid sequence has been deduced by molecular biology techniques.
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Affiliation(s)
- D Medynski
- Department of Pathology, Harvard Medical School, Boston, MA 02115
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166
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Identification of a sequence within the C-terminal 26 amino acids of cholesteryl ester transfer protein responsible for binding a neutralizing monoclonal antibody and necessary for neutral lipid transfer activity. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)37066-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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167
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De Sutter K, Remaut E, Fiers W. Disulphide bridge formation in the periplasm of Escherichia coli: beta-lactamase:: human IgG3 hinge fusions as a model system. Mol Microbiol 1992; 6:2201-8. [PMID: 1406260 DOI: 10.1111/j.1365-2958.1992.tb01394.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We report the construction and the expression in Escherichia coli of three different fusion genes encoding the extended human IgG3 hinge region (Hi) fused in-phase to the C-terminal end of bacterial TEM1 beta-lactamase (Bla). In the first fusion gene blahi, TEM1 beta-lactamase (Bla). In the first fusion gene blahi, the hinge sequence was directly coupled to the 3' end of the beta-lactamase gene, whereas in the two other constructs, blal1hi and blal2hi, a linker encoding 14 and 10 amino acids, respectively, was inserted between the two subunits. After expression (24 h, 20 degrees C) under control of the constitutive kanamycin phosphoribosyl transferase promoter, the fusion proteins, BlaHi, BlaL1Hi and BlaL2Hi, respectively, were almost exclusively detected in the periplasmic fraction, and they conferred carbenicillin-resistance to the cells. These results indicate that beta-lactamase can efficiently direct the export of proteins fused to its C-terminus, and moreover, at least some of the exported fusion proteins must carry the beta-lactamase moiety in a properly folded form. Analysis of their assembly, however, revealed that only a minor fraction was recovered as the expected F(ab')2-like dimer. The presence in the periplasm of 'oxidized' monomers (with intrachain disulphide bonds) as well as of several high-molecular-mass proteins, probably resulting from the association between monomers and other cysteine-rich proteins, strongly suggests that the conditions in the bacterial periplasm are insufficient to allow proper assembly of multimeric proteins with several interchain disulphide bonds.
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Affiliation(s)
- K De Sutter
- Laboratory of Molecular Biology, Gent University, Belgium
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168
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Gerstel B, Tuite MF, McCarthy JE. The effects of 5'-capping, 3'-polyadenylation and leader composition upon the translation and stability of mRNA in a cell-free extract derived from the yeast Saccharomyces cerevisiae. Mol Microbiol 1992; 6:2339-48. [PMID: 1406273 DOI: 10.1111/j.1365-2958.1992.tb01409.x] [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: 12/26/2022]
Abstract
A new modular expression system was developed to direct the in vitro synthesis of defined transcripts that were used as templates for translation in yeast cell-free extracts. The system was used to examine the influence of 5'-capping, 3'-polyadenylation and leader sequence upon the translation and stability of the synthetic Tn9 cat (chloramphenicol acetyl transferase), yeast PGK (phosphoglycerate kinase) and yeast HSP26 (heat-shock protein 26) mRNAs. The addition of a methylated cap (m7Gppp) or of a poly(A) tail enhanced translation and stabilized the mRNA. The dependence of translation upon capping was reduced in the presence of the HSP26 leader sequence. This may indicate the existence of a translational mechanism that enhances cap-independent translation. The enhancement of the translation and stability of mRNA was relatively insensitive to changes in the position of the poly(A) tail relative to the reading frame.
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Affiliation(s)
- B Gerstel
- Department of Gene Expression, Gesellschaft für Biotechnologische Forschung (GBF), Braunschweig, Germany
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169
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Flomenberg P, Szmulewicz J, Gutierrez E, Lupatkin H. Role of the adenovirus E3-19k conserved region in binding major histocompatibility complex class I molecules. J Virol 1992; 66:4778-83. [PMID: 1385834 PMCID: PMC241305 DOI: 10.1128/jvi.66.8.4778-4783.1992] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The adenovirus early region 3 glycoprotein E3-19k binds to and down regulates major histocompatibility complex (MHC) class I molecules in infected cells. We previously identified a 20-amino-acid conserved region in E3-19k by comparison of protein sequences from four different adenovirus serotypes. The roles of the E3-19k C-terminal and adjacent conserved regions in the interaction with MHC class I molecules have been examined. A functional class I-binding glycoprotein was expressed from the cloned E3 18.5-kDa open reading frame of adenovirus type 35. Truncations and single-amino-acid mutations in the adenovirus type 35 glycoprotein were created by site-directed in vitro mutagenesis and tested for the ability to associate with MHC class I molecules. Deletion of most of the transmembrane domain and cytoplasmic tail did not affect binding to class I molecules. However, removal of an additional 11 amino acids eliminated binding and changed the conformation of the adjacent conserved region. Separate mutations of residues Asp-107 and Met-110, within the conserved region, severely reduced or eliminated binding. These data indicate that the E3-19k conserved region plays a crucial role in binding to MHC class I molecules.
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Affiliation(s)
- P Flomenberg
- Department of Medicine, Medical College of Wisconsin, Milwaukee 53226
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170
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Tietze K, Oellers N, Knust E. Enhancer of splitD, a dominant mutation of Drosophila, and its use in the study of functional domains of a helix-loop-helix protein. Proc Natl Acad Sci U S A 1992; 89:6152-6. [PMID: 1631102 PMCID: PMC402140 DOI: 10.1073/pnas.89.13.6152] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Helix-loop-helix proteins play important roles in developmental processes, such as myogenesis, neurogenesis, and sex determination. The gene Enhancer of split [E(spl)] of Drosophila, a member of a gene complex that is involved in early neurogenesis, encodes a protein with a basic domain and a helix-loop-helix motif. We took advantage of a dominant mutation of this gene, E(spl)D, to define in vivo structural features of this protein for proper function. The mutation renders the otherwise recessive eye phenotype of spl dominant. By germ-line transformation of different in vitro mutagenized versions of the E(spl) gene, we could demonstrate that the basic domain of this helix-loop-helix protein is functional and necessary for expression of the dominant phenotype. These results are supported by in vitro DNA-binding assays, which showed that the basic domain is in fact necessary for DNA binding, despite the presence of a proline residue. Furthermore, we could show that the dominant enhancement of spl is caused by truncation of the E(SPL)D protein in combination with deletion of a putative regulatory element.
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Affiliation(s)
- K Tietze
- Institut für Entwicklungsbiologie, Universität zu Köln, Federal Republic of Germany
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171
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Killeen KP, Escuyer V, Mekalanos JJ, Collier RJ. Reversion of recombinant toxoids: mutations in diphtheria toxin that partially compensate for active-site deletions. Proc Natl Acad Sci U S A 1992; 89:6207-9. [PMID: 1631110 PMCID: PMC402151 DOI: 10.1073/pnas.89.13.6207] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Deleting an important active-site residue of diphtheria toxin, glutamic acid-148, reduces the toxin's ADP-ribosyltransferase activity by a factor of greater than 10(4). We considered using this mutation to construct a recombinant toxoid for expression by live attenuated vaccines and explored second-site mutations that might cause reversion. Activity was partially restored by substituting glutamic acid for valine-147 or by extending the deletion by five residues toward the NH2 terminus, thereby placing glutamic acid-142 immediately adjacent to tyrosine-149. In both mutants the indicated glutamic acid may occupy a spatial locus similar to that of glutamic acid-148 in the unmutated protein. Simply deleting a crucial residue does not, therefore, provide confidence that a second-site mutation could not readily restore activity to a toxoid.
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Affiliation(s)
- K P Killeen
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA
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172
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Despons L, Senger B, Fasiolo F, Walter P. Binding of the yeast tRNA(Met) anticodon by the cognate methionyl-tRNA synthetase involves at least two independent peptide regions. J Mol Biol 1992; 225:897-907. [PMID: 1602489 DOI: 10.1016/0022-2836(92)90409-d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
As for Escherichia coli methionine tRNAs, the anticodon triplet of yeast tRNA(Met) plays an important role in the recognition by the yeast methionyl-tRNA synthetase (MetRS), indicating that this determinant for methionine identity is conserved in yeast. Efficient aminoacylation of the E. coli tRNA(Met) transcript by the heterologous yeast methionine enzyme also suggests conservation of the protein determinants that interact with the CAU anticodon sequence. We have analysed by site-directed mutagenesis the peptide region 655 to 663 of the yeast MetRS that is equivalent to the anticodon binding region of the E. coli methionine enzyme. Only one change, converting Leu658 into Ala significantly reduced tRNA aminoacylation. Semi-conservative substitutions of L658 allow a correlation to be drawn between side-chain volume of the hydrophobic residue at this site and activity. The analysis of the L658A mutant shows that Km is mainly affected. This suggests that the peptide region 655 to 663 contributes partially to the binding of the anticodon, since separate mutational analysis of the anticodon bases shows that kcat is the most critical parameter in the recognition of tRNA(Met) by the yeast synthetase. We have analysed the role of peptide region (583-GNLVNR-588) that is spatially close to the region 655 to 663. Replacements of residues N584 and R588 reduces significantly the kcat of aminoacylation. The peptide region 583-GNLVNR-588 is highly conserved in all MetRS so far sequenced. We therefore propose that the hydrogen donor/acceptor amino acid residues within this region are the most critical protein determinants for the positive selection of the methionine tRNAs.
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Affiliation(s)
- L Despons
- Unité Structure des Macromolécules Biologiques et Mécanismes de Reconnaissance IBMC du CRNS, Strasbourg, France
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173
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Oertel-Buchheit P, Porte D, Schnarr M, Granger-Schnarr M. Isolation and characterization of LexA mutant repressors with enhanced DNA binding affinity. J Mol Biol 1992; 225:609-20. [PMID: 1602473 DOI: 10.1016/0022-2836(92)90389-2] [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: 12/27/2022]
Abstract
The LexA repressor from Escherichia coli is a sequence-specific DNA binding protein that shows no pronounced sequence homology with any of the known structural motifs involved in DNA binding. Since little is known about how this protein interacts with DNA, we have selected and characterized a great number of intragenic, second-site mutations which restored at least partially the activity of LexA mutant repressors deficient in DNA binding. In 47 cases, the suppressor effect of these mutations was due to an Ind- phenotype leading presumably to a stabilization of the mutant protein. With one exception, these second-site mutations are all found in a small cluster (amino acid residues 80 to 85) including the LexA cleavage site between amino acid residues 84 and 85 and include both already known Ind- mutations as well as new variants like GN80, GS80, VL82 and AV84. The remaining 26 independently isolated second-site suppressor mutations all mapped within the amino-terminal DNA binding domain of LexA, at positions 22 (situated in the turn between helix 1 and helix 2) and positions 57, 59, 62, 71 and 73. These latter amino acid residues are all found beyond helix 3, in a region where we have previously identified a cluster of LexA (Def) mutant repressors. In several cases the parental LexA (Def) mutation has been removed by subcloning or site-directed mutagenesis. With one exception, these LexA variants show tighter in vivo repression than the LexA wild-type repressor. The most strongly improved variant (LexA EK71, i.e. Glu71----Lys) that shows an about threefold increased repression rate in vivo, was purified and its binding to a short consensus operator DNA fragment studied using a modified nitrocellulose filter binding assay. As expected from the in vivo data, LexA EK71 interacts more tightly with both operator and (more dramatically) with non-operator DNA. A determination of the equilibrium association constants of LexA EK71 and LexA wild-type as a function of monovalent salt concentration suggests that LexA EK71 might form an additional ionic interaction with operator DNA as compared to the LexA wild-type repressor. A comparison of the binding of LexA to a non-operator DNA fragment further shows that LexA interacts with the consensus operator very selectively with a specificity factor of Ks/Kns of 1.4 x 10(6) under near-physiological salt conditions.
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Affiliation(s)
- P Oertel-Buchheit
- Institut de Biologie Moléculaire et Cellulaire, CNRS UPR 6201 affiliated to INSERM, Strasbourg, France
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174
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A common sequence motif, -E-G-Y-A-T-A-, identified within the primase domains of plasmid-encoded I- and P-type DNA primases and the alpha protein of the Escherichia coli satellite phage P4. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42381-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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175
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Ritchings BW, Lewin AS. Mutational evidence for competition between the P1 and the P10 helices of a mitochondrial group I intron. Nucleic Acids Res 1992; 20:2349-53. [PMID: 1375737 PMCID: PMC312352 DOI: 10.1093/nar/20.9.2349] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A guanosine to cytosine transversion at position 2 of the fifth intron of the mitochondrial gene COB blocks the ligation step of splicing. This mutation prevents the formation of a base pair within the P1 helix of this group I intron--the RNA duplex formed between the 3' end of the upstream exon and the internal guide sequence. The mutation also reduces the rate of the first step of splicing (guanosine addition at the 5' splice junction) while stimulating hydrolysis at the 3' intron-exon boundary. Consequently, the ligation of exons is blocked because the 3' exon is removed prior to cleavage at the 5' splice junction. The lesion can be suppressed by second-site mutations that preserve the potential for base-pairing at this position. Because the P1 duplex and the P10 duplex (between the guide sequence and the 3' exon) overlap at the affected pairings represent alternative structures that do not, indeed cannot, form simultaneously.
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Affiliation(s)
- B W Ritchings
- Department of Immunology and Medical Microbiology, University of Florida College of Medicine, Gainesville 32610
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176
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Komori M, Kikuchi O, Kitada M, Kamataki T. Molecular cloning of monkey P450 1A1 cDNA and expression in yeast. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1131:23-9. [PMID: 1581357 DOI: 10.1016/0167-4781(92)90093-f] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Monkey P450 1A1 cDNA (MKah1) was isolated from the lambda gt11 cDNA library of a liver from a 3-methylcholanthrene (3MC)-treated crab-eating monkey using a dog P450 1A1 cDNA fragment as a probe. MKah1 was 2453 bp long and contained an entire coding region for a polypeptide of 512 residues. The nucleotide and deduced amino acid sequences of MKah1 displayed 95% and 94% identity with those of the human P450 1A1 gene, respectively. Even in the 3' noncoding region, MKah1 showed 94% homology with human P450 1A1, whereas it showed less than 69% homology with other mammalian P450 1A1. Monkey P450 1A1 mRNA was not detectable in untreated livers, but was induced by polychlorinated biphenyl and 3MC. The expression plasmid (designated as pMKC-1) was constructed by introduction of the coding region of MKah1 into a yeast expression vector (pAM82) containing the promoter of acid phosphatase (APase). Northern blot analysis revealed that monkey P450 1A1 mRNA was expressed in yeast under the control of the APase promoter. Microsomes from yeast transformed by pMKC-1 catalyzed 7-ethoxycoumarin O-deethylation, benzo(a)pyrene hydroxylation and the mutagenic activation of 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 3-amino-1-methyl-5H-pyrido(4,3-b)-indole acetate (Trp-P-2) and 2-amino-6-methyldipyrido(1,2-a:3',2'-d)imidazole acetate (Glu-P-1).
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Affiliation(s)
- M Komori
- Division of Analytical Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Japan
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177
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Delling U, Reid LS, Barnett RW, Ma MY, Climie S, Sumner-Smith M, Sonenberg N. Conserved nucleotides in the TAR RNA stem of human immunodeficiency virus type 1 are critical for Tat binding and trans activation: model for TAR RNA tertiary structure. J Virol 1992; 66:3018-25. [PMID: 1560535 PMCID: PMC241061 DOI: 10.1128/jvi.66.5.3018-3025.1992] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Interaction between the human immunodeficiency virus type 1 (HIV-1) trans-activator Tat and its cis-acting responsive RNA element TAR is necessary for activation of HIV-1 gene expression. We investigated the hypothesis that the essential uridine residue at position 23 in the bulge of TAR RNA is involved in intramolecular hydrogen bonding to stabilize an unique RNA structure required for recognition by Tat. Nucleotide substitutions in the two base pairs of the TAR stem directly above the essential trinucleotide bulge that maintain base pairing but change sequence prevent complex formation with Tat in vitro. Corresponding mutations tested in a trans-activation assay strongly affect the biological activity of TAR in vivo, suggesting an important role for these nucleotides in the Tat-TAR interaction. On the basis of these data, a model is proposed which implicates uridine 23 in a stable tertiary interaction with the GC pair directly above the bulge. This interaction would cause widening of the major groove of the RNA, thereby exposing its hydrogen-bonding surfaces for possible interaction with Tat. The model also predicts a gap between uridine 23 and the first base pair in the stem above, which would require one or more unpaired nucleotides to close, but does not predict any other role for such nucleotides. In accordance with this prediction, synthetic propyl phosphate linkers of equivalent length to 1 or 2 nucleotides, were found to be fully acceptable substitutes in the bulge above uridine 23, demonstrating that neither the bases nor the ribose moieties at these positions are implicated in the recognition of TAR RNA by Tat.
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Affiliation(s)
- U Delling
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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178
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Dedieu JF, Ronco J, van der Werf S, Hogle JM, Henin Y, Girard M. Poliovirus chimeras expressing sequences from the principal neutralization domain of human immunodeficiency virus type 1. J Virol 1992; 66:3161-7. [PMID: 1373205 PMCID: PMC241080 DOI: 10.1128/jvi.66.5.3161-3167.1992] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sequences from the principal neutralization domain of human immunodeficiency virus type 1 (HIV-1) strain LAI or RF have been expressed in antigenic site 1 of the capsid of the Sabin strain of poliovirus type 1. A number of the resulting chimeras were viable. Viable variants bearing mutations within the insertion site spontaneously arose from several nonviable chimeras. In general, these mutations result in a decrease in positive charge in the substituted antigenic site 1. Two of the chimeras were genetically stable and have been further characterized. Both chimeras were neutralized by various HIV-1 neutralizing antibodies. In rabbits, both chimeras produced high levels of antibodies which react with HIV-1 gp120/160 in immunoprecipitation and enzyme-linked immunosorbent assays. One of the chimeras (HIV-1LAI) produced a significant but weak HIV-1 neutralizing response.
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Affiliation(s)
- J F Dedieu
- Unité de Virologie Moléculaire (Centre National de la Recherche Scientifique UA 545), Institut Pasteur, Paris, France
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179
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Vonèche V, Portetelle D, Kettmann R, Willems L, Limbach K, Paoletti E, Ruysschaert JM, Burny A, Brasseur R. Fusogenic segments of bovine leukemia virus and simian immunodeficiency virus are interchangeable and mediate fusion by means of oblique insertion in the lipid bilayer of their target cells. Proc Natl Acad Sci U S A 1992; 89:3810-4. [PMID: 1315040 PMCID: PMC525580 DOI: 10.1073/pnas.89.9.3810] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Modified bovine leukemia virus (BLV) glycoproteins were expressed by using vaccinia virus recombinants, and their fusogenic capacities were examined by a syncytia-formation assay. This analysis indicates that (i) both BLV envelope glycoproteins gp51 and gp30 are necessary for cell fusion; (ii) insertion of the N-terminal segment of gp30 (fusion peptide) into the lipid bilayer in an oblique orientation, as predicted by computer conformational analysis, results in fusogenic capacities higher than insertion in a perpendicular or parallel orientation; and (iii) replacement of the BLV fusion peptide with its simian immunodeficiency virus counterpart does not modify the fusogenic capacity of the BLV glycoprotein.
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Affiliation(s)
- V Vonèche
- Faculty of Agronomy, Gembloux, Belgium
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180
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Steczko J, Donoho GP, Clemens JC, Dixon JE, Axelrod B. Conserved histidine residues in soybean lipoxygenase: functional consequences of their replacement. Biochemistry 1992; 31:4053-7. [PMID: 1567851 DOI: 10.1021/bi00131a022] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Sequences of 13 lipoxygenases from various plant and mammalian species, thus far reported, display a motif of 38 amino acid residues which includes 5 conserved histidines and a 6th histidine about 160 residues downstream. These residues occur at positions 494, 499, 504, 522, 531, and 690 in soybean lipoxygenase isozyme L-1. Since the participation of iron in the lipoxygenase reaction has been established and existing evidence based on Mössbauer and EXAFS spectroscopy suggests that histidines may be involved in iron binding, the effect of the above residues has been examined in soybean lipoxygenase L-1. Six singly mutated lipoxygenases have been produced in which each of the His residues has been replaced with glutamine. Two additional mutants have been constructed wherein the codons for His-494 and His-504 have been replaced by serine codons. All of the mutant lipoxygenases, which were obtained by expression in Escherichia coli, have mobilities identical to that of the wild-type enzyme on denaturing gel electrophoresis and respond to lipoxygenase antibodies. The mutated proteins H499Q, H504Q, H504S, and H690Q are virtually inactive, while H522Q has about 1% of the wild-type activity. H494Q, H494S, and H531Q are about 37%, 8%, and 20% as active as the wild type, respectively. His-517 is conserved in the several lipoxygenase isozymes but not in the animal isozymes. The mutant H517Q has about 33% of the wild-type activity. The inactive mutants, H499Q, H504Q, H504S, and H690Q, become insoluble when heated for 3 min at 65 degrees C, as does H522Q. The other mutants and the wild-type are stable under these conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Steczko
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153
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181
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Sancho J, Fersht AR. Dissection of an enzyme by protein engineering. The N and C-terminal fragments of barnase form a native-like complex with restored enzymic activity. J Mol Biol 1992; 224:741-7. [PMID: 1569553 DOI: 10.1016/0022-2836(92)90558-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A method is described for producing fragments of a protein suitable for studies of protein folding. The codon for a single methionine residue is introduced into the cloned gene of barnase, and the gene product cleaved with cyanogen bromide. The site of mutation was chosen to be at the surface of the protein in a region connecting segments of secondary structure in the native enzyme. The alpha + beta protein was mutated from Val36----Met, and split into two fragments, B(1-36) containing the alpha-helical regions and B(37-110), the beta-sheet. The fragments were purified by ion exchange chromatography. Neither retains catalytic activity. Fluorescence, circular dichroism, and 1H nuclear magnetic resonance data indicate that their structures are each close to that of random-coil peptides. The two fragments associate to form a tight complex (Kd = 0.2 to 0.6 microM), which displays spectroscopic properties similar to those of the uncleaved protein. The catalytic activity is restored in the complex with a value for Km similar to that for native enzyme but with kcat reduced about three- to fourfold. The second-order rate constant for association on mixing fragments in the concentration range 2.5 to 7.5 microM is 1 x 10(5) s-1 M-1.
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Affiliation(s)
- J Sancho
- Department of Chemistry, University of Cambridge, U.K
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182
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Serrano L, Kellis JT, Cann P, Matouschek A, Fersht AR. The folding of an enzyme. II. Substructure of barnase and the contribution of different interactions to protein stability. J Mol Biol 1992; 224:783-804. [PMID: 1569557 DOI: 10.1016/0022-2836(92)90562-x] [Citation(s) in RCA: 312] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Barnase is described anatomically in terms of its substructures and their mode of packing. The surface area of hydrophobic residues buried on formation and packing of the structural elements has been calculated. Changes in stability have been measured for 64 mutations, 41 constructed in this study, strategically located over the protein. The purpose is to provide: (1) information on the magnitudes of changes in stabilization energy for mutations of residues that are important in maintaining the structure; and (2) probes for the folding pathway to be used in subsequent studies. The majority of mutations delete functional moieties of side-chains or make isosteric changes. The energetics of the interactions are variable and context-dependent. The following general conclusions may be drawn, however, from this study about the classes of interactions that stabilize the protein. (1) Truncation of buried hydrophobic side-chains has, in general, the greatest effect on stability. For fully buried residues, this averages at 1.5 kcal mol-1 per methylene group with a standard deviation of +/- 0.6 kcal mol-1. Truncation of partly exposed leucine, isoleucine or valine residues that are in the range of 50 to 80 A2 of solvent-accessible area (30 to 50% of the total solvent-accessible area on a Gly-X-Gly tripeptide, i.e. those packed against the surface) has a smaller, but relatively constant effect on stability, at 0.81 kcal mol-1 per methylene group with a statistical standard deviation of +/- 0.18 kcal mol-1. (2) There is a very poor correlation between hydrophobic surface area buried and the free energy change for an extensive data set of hydrophobic mutants. The best correlation is found to be between the free energy change and the number of methylene groups within a 6 A radius of the hydrophobic groups deleted. (3) Burial of the hydroxyl group of threonine in a pocket that is intended for a gamma-methyl group of valine costs 2.5 kcal mol-1, in the range expected for the loss of two hydrogen bonds.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- L Serrano
- Department of Chemistry, University of Cambridge, U.K
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183
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Meinnel T, Schmitt E, Mechulam Y, Blanquet S. Structural and biochemical characterization of the Escherichia coli argE gene product. J Bacteriol 1992; 174:2323-31. [PMID: 1551850 PMCID: PMC205854 DOI: 10.1128/jb.174.7.2323-2331.1992] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The DNA sequence of a 2,100-bp region containing the argE gene from Escherichia coli has been determined. The nucleotide sequence of the ppc-argE intergenic region was also solved and shown to contain six tandemly repeated REP sequences. Moreover, the oxyR gene has been mapped on the E. coli chromosome and shown to flank the arg operon. The codon responsible for the translation start of argE was determined by using site-directed mutants. This gene spans 1,400 bp and encodes a 42,350-Da polypeptide. The argE3 allele and a widely used argE amber gene have also been cloned and sequenced. N-Acetylornithinase, the argE product, has been overproduced and purified to homogeneity. Its main biochemical and catalytic properties are described. Moreover, we demonstrate that the protein is composed of two identical subunits. Finally, the amino acid sequence of N-acetylornithinase is shown to display a high degree of identity with those of the succinyldiaminopimelate desuccinylase from E. coli and carboxypeptidase G2 from a Pseudomonas sp. It is proposed that this carboxypeptidase might be responsible for the acetylornithinase-related activity found in the Pseudomonas sp.
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Affiliation(s)
- T Meinnel
- Laboratoire de Biochimie, Unité de Recherche Associée no. 240, Centre National de la Recherche Scientifique, Palaiseau, France
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184
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Hoe M, Hunt R. Loss of one asparagine-linked oligosaccharide from human transferrin receptors results in specific cleavage and association with the endoplasmic reticulum. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42918-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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185
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Park D, Plapp B. Interconversion of E and S isoenzymes of horse liver alcohol dehydrogenase. Several residues contribute indirectly to catalysis. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42798-6] [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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186
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Skorupski K, Pierce JC, Sauer B, Sternberg N. Bacteriophage P1 genes involved in the recognition and cleavage of the phage packaging site (pac). J Mol Biol 1992; 223:977-89. [PMID: 1538406 DOI: 10.1016/0022-2836(92)90256-j] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The packaging of bacteriophage P1 DNA is initiated by cleavage of the viral DNA at a specific site, designated pac. The proteins necessary for that cleavage, and the genes that encode those proteins, are described in this report. By sequencing wild-type P1 DNA and DNA derived from various P1 amber mutants that are deficient in pac cleavage, two distinct genes, referred to as pacA and pacB, were identified. These genes appear to be coordinately transcribed with an upstream P1 gene that encodes a regulator of late P1 gene expression (gene 10). pacA is located upstream from pacB and contains the 161 base-pair pac cleavage site. The predicted sizes of the PacA and PacB proteins are 45 kDa and 56 kDa, respectively. These proteins have been identified on SDS-polyacrylamide gels using extracts derived from Escherichia coli cells that express these genes under the control of a bacteriophage T7 promoter. Extracts prepared from cells expressing both PacA and PacB are proficient for site-specific cleavage of the P1 packaging site, whereas those lacking either protein are not. However, the two defective extracts can complement each other to restore functional pac cleavage activity. Thus, PacA and PacB are two essential bacteriophage proteins required for recognition and cleavage of the P1 packaging site. PacB extracts also contain a second P1 protein that is encoded within the pacB gene. We have identified this protein on SDS-polyacrylamide gels and have shown that it is translated in the same reading frame as is PacB. Its role, if any, in pac cleavage is yet to be determined.
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Affiliation(s)
- K Skorupski
- Du Pont Merck Pharmaceutical Co., Du Pont Experimental Station, Wilmington, DE 19880-0328
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187
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Sakowicz R, Kallwass H, Parris W, Gold M, Jones JB. THR246 mutations decrease substrate inhibition in lactate dehydrogenase. Biochem Biophys Res Commun 1992; 182:1309-12. [PMID: 1540173 DOI: 10.1016/0006-291x(92)91875-q] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Threonine 246 in Bacillus stearothermophilus L-lactate dehydrogenase has been changed to valine, serine, and alanine by site-directed mutagenesis. Kinetic analyses show a decrease in substrate inhibition for pyruvate reduction with the T246S mutant and virtual elimination of substrate inhibition for the T246A and T246V mutants. The results indicate that the absence of substrate inhibition in the 246A/V-catalyzed reactions is due to the elimination of a key hydrogen bond between the hydroxyl group of threonine and pyruvate in the wild-type complex that is an important contributor in the formation of the abortive enzyme-NAD(+)-pyruvate complex responsible for substrate inhibition.
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Affiliation(s)
- R Sakowicz
- Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada
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188
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Finck-Barbançon V, Prevost G, Mazurier I, Piemont Y. A structurally novel staphylococcal protein A from the V8 strain. FEMS Microbiol Lett 1992. [DOI: 10.1111/j.1574-6968.1992.tb05175.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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189
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Sheff DR, Rubenstein PA. Amino-terminal processing of actins mutagenized at the Cys-1 residue. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)45933-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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190
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Inagaki N, Maekawa T, Sudo T, Ishii S, Seino Y, Imura H. c-Jun represses the human insulin promoter activity that depends on multiple cAMP response elements. Proc Natl Acad Sci U S A 1992; 89:1045-9. [PMID: 1310538 PMCID: PMC48382 DOI: 10.1073/pnas.89.3.1045] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Glucose is known to increase the cAMP concentration in pancreatic beta cells. To determine the mechanism by which cAMP augments insulin gene expression, we first identified the cAMP response elements (CREs) of the human insulin gene. In DNase I footprint analysis, the bacterially synthesized CRE-binding protein, CRE-BP1, protected four sites: two sites in the region upstream from the insulin core promoter, one site in the first exon, and one site in the first intron. To examine the roles of those four sites, we constructed a series of DNA plasmids in which the wild-type and mutant insulin promoters were linked to the chloramphenicol acetyl-transferase gene. Studies of the transcriptional activity of these plasmids after transfection into hamster insulinoma (HIT) cells showed that these four sites contributed additively to the cAMP inducibility of the insulin promoter. Surprisingly, the c-jun protooncogene product (c-Jun) repressed the cAMP-induced activity of the insulin promoter in a cotransfection assay with the c-Jun expression plasmid. Northern blot analysis demonstrated that the level of c-jun mRNA was dramatically increased by glucose deprivation in HIT cells. These results suggest that glucose may regulate expression of the human insulin gene through multiple CREs and c-Jun.
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Affiliation(s)
- N Inagaki
- Department of Medicine, Kyoto University School of Medicine, Japan
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191
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Imanaka T, Nakae M, Ohta T, Takagi M. Design of temperature-sensitive penicillinase repressors by replacement of Pro in predicted beta-turn structures. J Bacteriol 1992; 174:1423-5. [PMID: 1735729 PMCID: PMC206442 DOI: 10.1128/jb.174.4.1423-1425.1992] [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: 12/28/2022] Open
Abstract
Pro residues in predicted beta-turn structures were substituted with other amino acids to obtain temperature-sensitive penicillinase repressors (PenI). A mutant repressor (P70L; Pro-70 is substituted with Leu) was inactive at 48 degrees C and penP gene expression was derepressed (1,200 U/OD660 [optical density at 660 nm] ), although the mutant was still active at 30 degrees C (27 U). The heat induction ratio (penicillinase activity at 48 degrees C compared with that at 30 degrees C) of the mutant was 98 times higher than that of the wild type (i.e., 44 versus 0.45). This result indicated that the side chain of the Leu residue in P70L destroyed the proper folding of the repressor protein at the elevated temperature, whereas the Pro residue of the wild-type repressor stabilized this predicted beta-turn structure even at 48 degrees C. When the Pro residue was replaced by amino acid residues with smaller side chains (i.e., Gly and Ala), these mutant repressors were less temperature sensitive than P70L. These data suggest that the presence of the Pro residue in the beta-turn structure could be one of the key factors in stabilizing protein structure at elevated temperatures.
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Affiliation(s)
- T Imanaka
- Department of Biotechnology, Faculty of Engineering, Osaka University, Japan
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192
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Tokunaga M, Kawamura A, Omori A, Hishinuma F. Structure of yeast pGKL 128-kDa killer-toxin secretion signal sequence. Processing of the 128-kDa killer-toxin-secretion-signal-alpha-amylase fusion protein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 203:415-23. [PMID: 1735428 DOI: 10.1111/j.1432-1033.1992.tb16565.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The linear double-stranded DNA plasmid pGKL1 in yeast encodes a killer toxin consisting of 97-kDa, 31-kDa and 28-kDa subunits. A 128-kDa protein precursor of the 97-kDa and 31-kDa subunits, was first synthesized with a 29-amino-acid extension at its NH2-terminus as a secretion signal sequence. In the present study, the property of this signal sequence was studied by the analysis of a fusion protein with mouse alpha-amylase. Using the secretion signal sequence of the killer protein, the mouse alpha-amylase was successfully secreted into the culture medium. An intracellular precursor form of alpha-amylase was identified and purified. Analysis of the NH2-terminal sequence of this precursor molecule indicated that it corresponded to the secretory intermediate (pro form) of alpha-amylase with the removal of the hydrophobic segment (Met1-Gly16) of the secretion signal. Both the secretion of alpha-amylase into the culture medium and the detection of the pro-alpha-amylase species in the cells were prohibited by a sec 11 mutation, or by the conversion of Gly to Val at the 16th position of the secretion signal. These results strongly suggest that the cleavage occurs between Gly16 and Leu17 by a signal peptidase, and that this cleavage is required for the secretion of alpha-amylase into the medium. Based on the data from the NH2-terminal amino acid sequences of secreted alpha-amylases, we conclude that the 29-amino-acid secretion signal present in the 128-kDa killer toxin precursor protein is a prepro structure.
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Affiliation(s)
- M Tokunaga
- Laboratories of Molecular Genetics, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan
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193
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Ellman JA, Mendel D, Schultz PG. Site-specific incorporation of novel backbone structures into proteins. Science 1992; 255:197-200. [PMID: 1553546 DOI: 10.1126/science.1553546] [Citation(s) in RCA: 148] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A number of unnatural amino acids and amino acid analogs with modified backbone structures were substituted for alanine-82 in T4 lysozyme. Replacements included alpha,alpha-disubstituted amino acids, N-alkyl amino acids, and lactic acid, an isoelectronic analog of alanine. The effects of these electronic and structural perturbations on the stability of T4 lysozyme were determined. The relatively broad substrate specificity of the Escherichia coli protein biosynthetic machinery suggests that a wide range of backbone and side-chain substitutions can be introduced, allowing a more precise definition of the factors affecting protein stability.
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Affiliation(s)
- J A Ellman
- Department of Chemistry, University of California, Berkeley 94720
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194
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Veidt I, Bouzoubaa SE, Leiser RM, Ziegler-Graff V, Guilley H, Richards K, Jonard G. Synthesis of full-length transcripts of beet western yellows virus RNA: messenger properties and biological activity in protoplasts. Virology 1992; 186:192-200. [PMID: 1727597 DOI: 10.1016/0042-6822(92)90073-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Full-length cDNA of beet western yellows virus genomic RNA has been cloned behind the bacteriophage T7 RNA polymerase promoter of the transcription vector BS(-). The in vitro run-off transcription product obtained in the presence of T7 RNA polymerase and m7GpppG cap has the same messenger properties as natural viral RNA in in vitro translation systems. The full-length transcript was also able to infect Chenopodium quinoa protoplasts inoculated by electroporation. Infection could be followed by the appearance of viral coat protein in the inoculated protoplasts and the de novo synthesis of viral RNA. Site-directed mutagenesis experiments revealed that expression of beet western yellows virus open reading frame 1 and the C-terminal portion of open reading frame 6 were not required for infection of protoplasts. Additional experiments with these mutants and mutants in the other viral open reading frames should provide information concerning the requirements for beet western yellows virus replication and, ultimately, the role of virus genes in other important steps in the virus infection cycle, such as aphid transmission.
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Affiliation(s)
- I Veidt
- Institute de Biologie Moléculaire des Plantes du CNRS, Strasbourg, France
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195
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Bullerjahn AM, Freisheim JH. Site-directed deletion mutants of a carboxyl-terminal region of human dihydrofolate reductase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48363-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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196
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Smith JF, Hawkins J, Leonard RE, Hanas JS. Structural elements in the N-terminal half of transcription factor IIIA required for factor binding to the 5S RNA gene internal control region. Nucleic Acids Res 1991; 19:6871-6. [PMID: 1762917 PMCID: PMC329322 DOI: 10.1093/nar/19.24.6871] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Zinc binding domains and the conserved Thr-Gly-Glu-Lys (TGEK) tetrapeptide in the N-terminal half of transcription factor IIIA (TFIIIA) were subjected to in vitro mutagenesis to biochemically assess their role in factor interaction with the 5S gene internal control region (ICR). TFIIIA containing a Leu in place of His33 in the Cys2His2 zinc binding site of finger I lost the ability to protect the entire 5S RNA gene ICR (nucleotides +96 to +43) from DNase I digestion. Thus, mutation of one potential zinc ligand in the N-terminal finger inhibited specific DNA binding by the N-terminal as well as downstream fingers. Cooperativity apparently exists among TFIIIA zinc fingers in metal binding/finger folding and DNA binding. Substituting a Ser for Gly69 or a Glu for Lys 71 in the conserved TGEK tetrapeptide in finger II of TFIIIA resulted in the loss of DNA binding. A Gly-dependent bend structure and a terminal positive charge in this tetrapeptide are important for TFIIIA interaction with DNA. Whereas TFIIIA with a Ser substituted for Cys20 in finger I (proposed zinc ligand) did not protect the ICR from DNase I digestion, TFIIIA containing a Ser substituted for Cys35 (not a proposed zinc ligand) retained the ability to bind the ICR. When Cys112 or Cys 164 (proposed zinc ligands in fingers IV and VI) were replaced by Ser, the DNase I footprint patterns afforded by the respective mutant proteins were similar, protection on the ICR from about nucleotides +96 up to +78. A similar pattern was obtained with a TFIIIA mutant in which fingers V, VI, VII, and a portion of VIII were deleted. Maintenance of zinc coordination spheres in necessary for DNA binding by downstream fingers. The six fingers comprising the N-terminal half of TFIIIA appear to act in two groups of three with binding of the second group dependent upon initial binding of the N-terminal group to the +90 to +80 region of the 5S gene ICR.
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Affiliation(s)
- J F Smith
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190
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197
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Abstract
A 2.1 kb (1 kb = 10(3) base-pairs) segment of DNA from the streptomycete bacteriophage phi C31 was found to be sufficient to direct site-specific integration of plasmid vectors in Streptomyces ambofaciens and Streptomyces fradiae in the absence of any streptomycete origin of replication. Sequencing and analysis of phage, chromosomal and junction attachment sites of S. ambofaciens and S. fradiae revealed that recombination is conservative and that crossover takes place within three bases of homology between phage and host. Deletion analysis, sequencing and site-specific mutagenesis of the phi C31 DNA revealed a large open reading frame (ORF 613) whose expression was necessary for integration. This ORF begins near the point of crossover and reads away from the attachment site. A comparison of the predicted amino acid sequence of ORF 613 with known recombinases did not reveal any significant similarities. A genetic analysis of the amino-terminal region of ORF 613 suggested that translation could initiate at any one of three possible start codons. Primer extension experiments showed that transcriptional initiation occurred at a T and a C only four and five bases, respectively, from the site of crossover. This analysis suggested that ORF 613 would be separated from its promoter upon integration.
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Affiliation(s)
- S Kuhstoss
- Lilly Research Laboratories Lilly Corporate Center, Indianapolis, IN 46285
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198
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Romero A, GarÄia P. Initiation of translation at AUC, AUA and AUU codons inEscherichia coli. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04618.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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199
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Zu Y, Maekawa T, Matsuda S, Ishii S. Complete putative metal finger and leucine zipper structures of CRE-BP1 are required for the E1A-induced trans-activation. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54404-5] [Citation(s) in RCA: 8] [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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200
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Zhou J, Doorbar J, Sun XY, Crawford LV, McLean CS, Frazer IH. Identification of the nuclear localization signal of human papillomavirus type 16 L1 protein. Virology 1991; 185:625-32. [PMID: 1660197 DOI: 10.1016/0042-6822(91)90533-h] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Human papillomavirus type 16(HPV16) L1 and L2 capsid proteins can be detected only in the nucleus of infected cells. For other nuclear proteins, specific sequences of basic amino acids(aa) termed nuclear localization signals (NLS) direct the protein from the cytoplasm to the nucleus. We used a series of deletion and substitution mutations of the HPV16 L1 protein, produced by recombinant vaccinia virus (rVV), to identify NLS within HPV16 L1 and showed that HPV16 L1 contains two NLS sequences, each containing basic aa clusters. One NLS consisted of 6 basic amino acids (KRKKRK from aa 525 to 530) at the carboxy terminal end of L1. The other NLS contained 2 basic aa clusters(KRK from aa 510 to 512 and KR at aa 525, 526) separated by 12 amino acids. Mutations in either NLS did not alter nuclear localization of L1 when the other remained intact, but mutations to both prevented nuclear localization of L1. The L1 NLS could be overridden by introduction of a membrane binding sequence at the amino terminal end of the protein. A databases search showed that all sequenced papillomaviruses are predicted to have L1 and L2 capsid proteins with sequences of basic amino acids homologous with one or both NLS of HPV16 L1.
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Affiliation(s)
- J Zhou
- Department of Medicine, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia
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