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Design and Synthesis of Semisynthetic Enzymes.
Annual rept. Aug 86-Jul 87,
CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
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We propose to develop methodology which will for the first time enable specific amino acid residues in proteins to be site-specifically replaced with synthetic amino acid analogues. Amino acids with novel steric, electronic, or spectroscopic properties will then be used to probe structure-function relationships in proteins which lead to receptorsubstrate recognition andor catalysis. We are pursuing a combined chemicalgenetic strategy toward this objective. Our approach requires replacement of the codon for the target amino acid with an amber nonsense codon 5-TAG-3 via oligonucleotide-directed mutagenesis. A nonsense suppressor RNA that recognizes this unique blank codon is being constructed by both anticodon loop replacement and by chemical synthesis and overproduction E. coli of an amber suppressor gene, using known chemicalbiological procedures. This suppressor RNA will then be chemically aminoacylated with novel amino acids by existing chemical methods, thereby avoiding the natural specificity of the aminoacyl RNA synthetases. The aminoacylated RNA will be used as a delivery vehicle in vitro for placing novel synthetic amino acids site-specifically into proteins. The methodology described above will be developed and optimized with the enzyme, Beta-lactamase, which catalyzes the hydrolysis of the Beta-lactam antibiotics penicillin and cephalosporin.
APPROVED FOR PUBLIC RELEASE