Elucidation of the Geometric Properties of the Pdu Microcompartment by Cryo-Electron Tomography

Presented During:

07/30/2022: 5:30 PM - 7:30 PM
Portland Marriott Downtown Waterfront  


2022: 72nd ACA Annual Meeting

Session Type:


Presenting Author :

Kevin Cannon  

Additional Author(s):

Todd Yeates  
University of California Los Angeles
Jessica Ochoa  
California Institute of Technology
Justin Miller  
James Evans  
Pacific Northwest National Lab
Trevor Moser  
Pacific Northwest National Lab

Abstract Body:

Approximately 20% of all bacteria contain giant supramolecular structures called bacterial microcompartments, or MCPs. MCPs are organelle-like structures that carry out various metabolic functions and are composed of a large proteinaceous shell that encapsulates enzymes and other proteins. These shells are roughly polyhedral in shape and consist of tessellating hexameric, pentameric and trimeric protein oligomers. Besides organizing an interior space inside the cell, the protein shell of an MCP plays a vital role in controlling diffusive transport of metabolic substrates and products from and to the cytosol. While some MCPs, such as carboxysomes, have been observed to have a nearly icosahedral shell, others have ambiguous geometries that have not been characterized in detail. Compared to carboxysomes, the 1,2-propanediol utilization (Pdu) microcompartment is a type of MCP that is more irregular in shape and size, with polyhedral properties that are not yet well-understood. Additionally, the hexagonally shaped protein oligomers that make up the shell of the Pdu MCP have distinct properties, with one side that is flat and one side that is dimpled. The native orientation of these shell proteins has not been confirmed in endogenous MCPs. We present ongoing efforts to use cryo-electron tomography (cryo-ET), combined with X-ray crystallographic data, to investigate these unsolved mysteries of the geometric shape of the Pdu MCP.

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