- Protein engineering by in vivo incorporation of non-natural amino acids: Control of incorporation of methionine analogues by methionyl-tRNA synthetase
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The incorporation of non-natural amino acids is an important strategy for engineering novel chemical and physical properties into natural and artificial proteins. The incorporation of amino acids into proteins in vivo is controlled in large part by the aminoacyl-tRNA synthetases (AARS). We have measured kinetic constants for in vitro activation of a set of methionine analogues by methionyl-tRNA synthetase (MetRS) via the ATP-PP(i) exchange reaction. Activation of methionine analogues in vitro correlates well with the ability of these analogues to support protein synthesis in vivo, substantiating the critical role of the AARS in controlling the incorporation of non-natural amino acids into proteins. Methionine analogues with k(cat)/K(m) values 2000-fold lower than those for methionine can support synthesis of a typical target protein (mDHFR) under standard conditions of protein expression. The kinetic constants correlate well with observed protein yields from a conventional bacterial expression host, indicating that the MetRS activity of the host can control the level of protein synthesis under certain conditions. Furthermore, increasing the MetRS activity of the bacterial host results in increased protein synthesis in media supplemented with the methionine analogues homoallylglycine and norleucine. These results suggest new strategies for incorporation of non-natural amino acids via manipulation of the AARS activity of a bacterial host. (C) 2000 Elsevier Science Ltd.
- Kiick, Kristi L.,Tirrell, David A.
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- Efficient incorporation of unsaturated methionine analogues into proteins in vivo
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A set of eight methionine analogues was assayed for translational activity in Escherichia coli. Norvaline and norleucine, which are commercially available, were assayed along with 2-amino-5-hexenoic acid (2), 2-amino-5-hexynoic acid (3), cis-2-amino-4-hexenoic acid (4), trans-2-amino-4-hexenoic acid (5), 6,6,6-trifluoro-2-aminohexanoic acid (6), and 2-aminoheptanoic acid (7), each of which was prepared by alkylation of diethyl acetamidomalonate with the appropriate tosylate, followed by hydrolysis. The E. coli methionine auxotroph CAG18491, transformed with plasmids pREP4 and pQE15, was used as the expression host, and translational activity was assayed by determination of the capacity of the analogue to support synthesis of the test protein dihydrofolate reductase (DHFR) in the absence of added methionine. The importance of amino acid side chain length was illustrated by the fact that neither norvaline (8) nor 7 showed translational activity, in contrast to norleucine (9), which does support protein synthesis under the assay conditions. The internal alkene functions of 4 and 5 prevented incorporation of these analogues into test protein, and the fluorinated analogue 6 yielded no evidence of translational activity. The terminally unsaturated compounds 2 and 3, however, proved to be excellent methionine surrogates: 1H NMR spectroscopy, amino acid analysis, and N-terminal sequencing indicated ~85% substitution of methionine by 2, while 3 showed 90-100% replacement. Both analogues also function efficiently in the initiation step of protein synthesis, as shown by their near-quantitative occupancy of the N-terminal amino acid site in DHFR. Enzyme kinetics assays were conducted to determine the rate of activation of each of the methionine analogues by methionyl tRNA synthetase (MetRS); results of the in vitro assays corroborate the in vivo incorporation results, suggesting that success or failure of analogue incorporation in vivo is controlled by MetRS.
- Van Hest, Jan C. M.,Kiick, Kristi L.,Tirrell, David A.
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- Amino acid stannous and application thereof in polyurethane foam
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The invention relates to the field of chemical engineering, and relates to an organic tin catalyst, in particular to amino acid stannous and an application thereof in preparation of polyurethane foam. According to the method, firstly, pyruvic acid and aldehyde serve as raw materials, amino acid is synthesized through three steps, and then the amino acid reacts with stannous oxide to prepare the amino acid stannous. Compared with traditional stannous carboxylate, only carboxyl in the traditional stannous carboxylate is coordinated with a tin center, while amido and carboxyl in the amino acid stannous provided by the invention are coordinated with the tin center at the same time, so that the complex is more stable and higher in catalytic activity. In addition, the method for synthesizing the amino acid is not reported in public literatures, and the method is cheap in reagent, simpler in formula, more convenient to operate, green, safe, efficient, environmentally friendly and suitable for industrial production.
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Paragraph 0020-0021; 0024-0026
(2021/11/27)
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- Enantioselective organocatalytic synthesis of 2-oxopiperazines from aldehydes: Identification of the elusive epoxy lactone intermediate
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An organocatalytic linchpin catalysis approach was envisaged to convert simple aldehydes into enantioenriched 2-oxopiperazines. A four-step reaction sequence (chlorination, oxidation, substitution, and cyclization) was developed and led to different substitution patterns in high yields and selectivities. The reaction mechanism was studied, and the previously elusive epoxy lactone intermediate was identified by HRMS.
- Kaplaneris, Nikolaos,Spyropoulos, Constantinos,Kokotou, Maroula G.,Kokotos, Christoforos G.
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supporting information
p. 5800 - 5803
(2016/11/29)
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- Peptides with an insulin-like action
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Peptides with an insulin-like action, of formula I: STR1 in which G is a hydrogen atom, an amino add residue, or a monosubstituted or polysubstituted amino acid; D is an amino acid residue, a phosphoamino acid residue, a monosaccharide residue, or a covalent bond; E is --NH--(CH2)n --NR52, a glycerol residue, or --NH--(CH2)p --R6 --R7 ; R1 is (C1 -C4)-alkyl or =O; R2 is a sulfhydryl protecting group, (C1 -C3)-alkyl, or a hydrogen atom; R3 and R4, independently of one another, are a hydrogen atom or methyl; R5, each being identical or different, is a hydrogen atom, 1 to 6 monosaccharide residues, or 1 to 6 monosubstituted or polysubstituted monosaccharide residues; R6 is O PO4 H, PO2 H, NHCOO, S or OCOO; R7 is a hydrogen atom, 1 to 6 monosaccharide residues, or 1 to 6 monosubstituted or polysubstituted monosaccharide residues; w is an integer 1 or 2; their preparation and use for treatment of diabetes mellitus or insulin-independent diabetes.
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