Encapsulins: molecular biology of the shell

Abstract

Compartmentalization is both a fundamental principle of cellular organization and an emerging theme in prokaryotic biology. Work in the past few decades has shown that protein-based organelles called microcompartments enhance the function of encapsulated cargo proteins. More recently, the repertoire of known prokaryotic organelles has expanded beyond microcompartments to include a new class of smaller proteinaceous compartments, termed nanocompartments (also known as encapsulins). Nanocompartments are icosahedral capsids that are smaller and less complex than microcompartments. Encapsulins are formed by a single species of shell protein that self-assembles and typically encapsulates only one type of cargo protein. Significant progress has been made in understanding the structure of nanocompartment shells and the loading of cargo to the interior. Recent analysis has also demonstrated the prevalence of encapsulin genes throughout prokaryotic genomes and documented a large diversity of cargo proteins with a variety of novel functions, suggesting that nanocompartments play an important role in many microbes. Here we review the current understanding of encapsulin structure and function and highlight exciting open questions of physiological significance.

Graphical Abstract

Keywords:

• Compartmentalization
• encapsulin
• nanocompartment
• bacterial organelle
• oxidative stress

Acknowledgements

We thank Rachel D. Hood and Avi Flamholz for helpful suggestions in the preparation of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant DE-SC00016240 (to D.F.S).