Multiple‐Site Labeling of Proteins with Unnatural Amino Acids

Abstract

A cell-free protein synthesis system from which the release factor RF1 has been selectively removed enables the facile incorporation of unnatural amino acids into proteins at difficult and multiple sites by optimized use of orthogonal tRNA/aminoacyl-tRNA synthetase systems. 19F NMR spectroscopy of a protein labeled combinatorially with trifluoromethyl phenylalanine (red in picture) at multiple sites establishes resonance assignments with a minimal number of samples.