Incorporation of proline analogs into recombinant proteins expressed in Escherichia coli

Proline residues are unique in the extent to which they constrain the conformational space available to the protein backbone. Because the conformational preferences of proline cannot be recapitulated by any of the other proteinogenic amino acids, standard mutagenesis approaches that seek to introduce new chemical functionality at proline positions unavoidably perturb backbone flexibility. Here, we detail the incorporation of proline analogs into recombinant proteins in Escherichia coli via a residue-specific mutagenesis strategy. This approach results in global replacement of proline residues with high yields of the recombinant protein of interest, minimal genetic manipulation, and maintenance of backbone conformational constraints.