Expression system for directly achieving fatty acid modification in protein translation process and application
A technology of expression system and translation process, applied in the field of pharmaceutical protein preparation
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Embodiment 1
[0054] Embodiment 1: chemical synthesis contains the hydrochloride or trifluoroacetate of HepoK
[0055]
[0056] α-N-Boc-lysine reacts with heptanoyl chloride under alkaline conditions to generate ε-N-heptanoyl-α-N-Boc-lysine, and removes the Boc protecting group under acidic conditions (TFA or HCl) , the corresponding ε-N-heptanoyl-lysine trifluoroacetate or hydrochloride was prepared and confirmed by nuclear magnetic resonance (NMR) (see Figure 4 ).
Embodiment 2
[0057] Embodiment 2: Construction of aminoacyl tRNA synthetase library
[0058] Genetically encoded unnatural amino acid technology (GEUAA) uses orthogonal tRNA / orthogonal aminoacyl tRNA-synthetase molecule pairs to recognize the amber stop codon (TAG) in living cells, and inserts unnatural amino acids into proteins at specific sites through ribosomes. The method of amino acids, and pyrrolysine is a representative of the principle used in nature. Therefore, the present invention uses the aminoacyl tRNA synthetase (PylRS) of Methanosarcina mazei pyrrolysine (Pyl) as a template, and according to the published crystal structure, adopts the degenerate primer mutation method to target Leu301 and Ala302 in the amino acid binding site. , Leu305, Tyr306, Leu309, Cys348 and other positions for saturation mutation, construct >10 8 library of aminoacyl tRNA synthetases (see Figure 5 ).
Embodiment 3
[0059] Embodiment 3: Screening of aminoacyl tRNA synthetase
[0060] The above aminoacyl tRNA synthetase library was screened using forward and reverse double selection methods,
[0061] 1) Forward screening: co-transfect Escherichia coli DH10β electrocompetent E. coli DH10β electrocompetent with the above synthetase library plasmid and the chloramphenicol resistance gene containing the amber stop codon (TAG) and the plasmid of the green fluorescent protein gene containing the TAG. Culture medium containing chloramphenicol and HepoK hydrochloride or trifluoroacetate (1 mM). If PylRS recognizes natural amino acids or HepoK, TAG can be read through, then the chloramphenicol resistance gene and green fluorescent protein are expressed, and E. coli survives and emits green fluorescence.
[0062] 2) Reverse screening: extract the PylRS plasmid in surviving Escherichia coli, and co-transfect Escherichia coli DH10β electrocompetent with the plasmid of the barnase toxin gene containin...
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