Date of Award
Master of Science
Biochemistry, Biophysics and Molecular Biology
Thomas A. Bobik
Bacterial microcompartments (MCPs) are proteinaceous sub-cellular organelles that are widely distributed among bacteria and that function in a variety of processes ranging from global carbon fixation to enteric pathogenesis. MCPs consist of metabolic enzymes encapsulated with a protein shell. The role of the MCP is to harbor a specific metabolic pathway that produces a toxic or volatile intermediate and confine that intermediate to minimize cellular toxicity and carbon loss. To date, the protein shells of MCPs have been shown to play a functional role in transport of small metabolites through selective pores and in the encapsulation of lumen enzymes through short N-or C-terminal peptide extensions. Interestingly, homologs of the propanediol utilization (Pdu) MCP shell protein PduB’ have been crystallized in two forms, one that is closed and another that forms a large channel. This suggested that these proteins undergo conformational changes that allow the transport of larger enzymatic cofactor that the MCP needs to properly function. However, no mutational work has been done to examine residues that are responsible for such a large conformational change and assess its physiological significance. Charged residues (R78, K81) and Ramachandran outlier (D79), which are located at the center of the PduB’, are key structural components that when substituted with alanine cause MCP instability. Interestingly, substitutions of a channel residue A53 appears to cause central pore opening. In addition, results indicate that there is a functional difference between PduB and PduB’ despite the fact that they are identical in sequence except for a 37 amino acid N-terminal extension on PduB. The smaller protein, PduB’, is dispensable for MCP formation but the PduB protein which contains a 37 amino acid N-terminal extension is integral to MCP assembly and formation.
Lehman, Brent, "Functional analysis of the propanediol utilization microcompartment shell proteins PduB and PduB' in Salmonella enterica" (2015). Graduate Theses and Dissertations. 14835.