Organelles designed for protein engineering

Abstract

Designer organelles might make it easier to produce engineered proteins in mammalian cells. Edward A. Lemke of the Johannes Gutenberg University Mainz’s Institute of Molecular Biology and the European Molecular Biology Laboratory and his coworkers have made artificial membraneless organelles from “assemblers” that are hybrids of truncated motor proteins that assemble on microtubules and proteins that phase separate above a minimum concentration (Science 2019, DOI: 10.1126/science.aaw2644). The two types of proteins assemble into structures that allow the simultaneous spatial and phase separation of the machinery needed for synthesizing proteins with nonnatural amino acids. That machinery includes the suppressor transfer RNA and tRNA synthetase needed for repurposing the Amber stop codon—a signal for cells to stop protein translation—as one that inserts nonnatural amino acids into proteins. The researchers also add a tag that steers the target messenger RNA to the organelle. This strategy enables the resea...