MicroProteins: Dynamic and accurate regulation of protein activity

Proteins usually assemble oligomers or high-order complexes to increase their efficiency and specificity in biological processes. The dynamic equilibrium of complex formation and disruption imposes reversible regulation of protein function. MicroProteins are small, single-domain proteins that directly bind target protein complexes and disrupt their assembly. Growing evidence shows that microProteins are efficient regulators of protein activity at the post-translational level. In the last few decades, thousands of plant microProteins have been predicted by computational approaches, but only a few have been experimentally validated. Recent studies highlighted the mechanistic working modes of newly-identified microProteins in Arabidopsis and other plant species. Here, we review characterized microProteins, including their biological roles, regulatory targets, and modes of action. In particular, we focus on microProtein-directed allosteric modulation of key components in light signaling pathways, and we summarize the biogenesis and evolutionary trajectory of known microProteins in plants. Understanding the regulatory mechanisms of microProteins is an important step towards potential utilization of microProteins as versatile biotechnological tools in crop bioengineering.