Prokaryotic nanocompartments, also known as encapsulins, are a recently discovered proteinaceous organelle-like compartments in prokaryotes that compartmentalize cargo enzymes. While initial studies have begun to elucidate the structure and physiological roles of encapsulins, bioinformatic evidence suggests that a great diversity of encapsulin nanocompartments remains unexplored. Here, we describe a novel encapsulin in the freshwater cyanobacterium Synechococcus elongatus PCC 7942. This nanocompartment is upregulated upon sulfate starvation and encapsulates a cysteine desulfurase enzyme via an N-terminal targeting sequence. Using cryo-electron microscopy, we have determined the structure of the nanocompartment complex to 2.2 Å resolution. Lastly, biochemical characterization of the complex demonstrated that the activity of the cysteine desulfurase is enhanced upon encapsulation. Taken together, our discovery, structural analysis, and enzymatic characterization of this prokaryotic nanocompartment provide a foundation for future studies seeking to understand the physiological role of this encapsulin in various bacteria.
Cryo-EM maps of holo and apo-SrpI have been deposited at the EM Data Resource with accession codes EMD-22094 and EMD-22095 respectively. The refined coordinate model has been deposited at the Protein Data Bank (PDB) with accession code 6X8M and 6X8T.
CryoEM SPA of Holo-SrpI Encapsulin Complex (Raw Frames)EMPIAR-10506.
CryoEM SPA of Apo-SrpI Encapsulin Complex (Raw Frames)EMPIAR-10510.
- Robert J Nichols
- Naiya R Phillips
- Luke M Oltrogge
- David F Savage
- Benjamin LaFrance
- Eva Nogales
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Sriram Subramaniam, University of British Columbia, Canada
© 2021, Nichols et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.