Congeneric bio-adhesive mussel foot proteins designed by modified prolines revealed a chiral bias in unnatural translation

Chiral bias in the unnatural translation and ‘sticky’ mussel proteins. The residue-specific in vivo incorporation of hydroxylated amino acids as well as other synthetic analogs, such as fluoroprolines, emerges as the method of choice for recombinant synthesis of Pro-rich mussel adhesive protein congeners. Chemical diversifications introduced in this way provide a general route towards bio-adhesive congeners endowed with properties not developed by natural evolution. Most importantly, we have found that the co-translational incorporation of (4R)-, and (4S)-hyroxylated and fluorinated analogs into mussel proteins presented a chiral bias: the expressed protein was only detectable in samples incubated with analogs with (4R)-substituents. Possible relationship of these stereochemical preferences for (4R)-stereoisomers in the translation to intracellular tRNA concentrations, ribosomal editing and proofreading or structural effects such as preorganization remains to be addressed in future studies. These studies will generally provide a mechanistic framework for the flexibility of the translational machinery and establish the boundaries of the unnatural translation.

Figure optionsDownload as PowerPoint slideHighlights
► Alternative translations of the gene sequence with synthetic amino acids – unnatural translation.
► Sensitivity of the translation machinery for stereochemical differences in the proline analogues.
► (4R)-/(4S)-hyroxylated and fluorinated analogs in Pro-rich sequences – a chiral bias.
► Stereochemical preferences for (4R)-stereoisomers in the translation with Pro-rich mussel proteins.
► Natural bio-material (‘bio-glue’) – for potential applications in biomedicine.