Tethered Ribosomes: Toward the Synthesis of Nonproteinogenic Polymers in Bacteria

Joining ribosomal subunits with a small RNA linker has recently given rise to tethered ribosomes. Their ability to process orthogonal mRNAs (o-mRNA) independent of endogenous ribosomes allowed the identification of otherwise lethal, gain-of-function mutations. Thus, engineering tethered ribosomes promises to significantly expand the scope of building blocks amenable to translation and, ultimately, enable the sequence-selective synthesis of tailor-made (bio)polymers.

Abstract

The ribosome is the core element of the translational apparatus and displays unrivaled fidelity and efficiency in the synthesis of long polymers with defined sequences and diverse compositions. Repurposing ribosomes for the assembly of nonproteinogenic (bio)polymers is an enticing prospect with implications for fundamental science, bioengineering and synthetic biology alike. Here, we review tethered ribosomes, which feature inseparable large and small subunits that can be evolved for novel function without interfering with native translation. Following a tutorial summary of ribosome structure, function, and biogenesis, we introduce design and optimization strategies for the creation of orthogonal and tethered ribosomes. We also highlight studies, in which (rational) engineering efforts of these designer ribosomes enabled the evolution of new functions. Lastly, we discuss future prospects and challenges that remain for the ribosomal synthesis of tailor-made (bio)polymers.

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