Incorporation of chlorinated analogues of aliphatic amino acids during cell-free protein synthesis

3-Chloro-Abu and 4-chloro-Nva are biosynthetically incorporated into E. coli peptidyl-Pro cis-trans isomerase B, as substitutes for Val and Leu, respectively. The extent of incorporation is up to 90%, and substituted protein is catalytically active. By contrast, 4-chloro-Val is not an effective replacement for Ile.