Abstract

CCT, a large (1 MDa) protein-folding machine, is a eukaryotic group II chaperonin that is essential for folding many cellular proteins and is the most complex of all chaperonins with two rings each composed of eight paralogous subunits. CCT captures proteins in its folding chamber to assist the folding of its substrates. CCT utilizes ATP hydrolysis to open and close its chamber and fold its substrates. CCT has been shown to be important in the folding of proteins with - propeller domains which consist of seven WD40 repeat sequences that fold into -sheets that form the blades of a propeller-like circular structure. One class of the substrates containing - propeller domains is the  subunit of heterotrimeric G proteins (G), which shuttles signals from GPCRs to effector enzymes and ion channels in various cell signaling processes. G subunits are known to be folded by the cytosolic chaperonin CCT with the aid of the cochaperone, phosducin-like protein 1 (PhLP1). Additionally, CCT has been known to bind several viral proteins and contribute to viral replication and production of HIV, hepatitis C, and reovirus. The core enzyme (non-structural protein 12, Nsp12) of the RNA-dependent RNA polymerase (RdRp) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported to interact with CCT; however, little is known of how CCT folds its substrates generally. Here, we employ structural and biochemical approaches to elucidate the CCT-mediated folding mechanisms of G protein 1 subunit (G1) and the G protein 5 subunit (G5). We further show how these proteins are released from CCT and assembled into their signaling partners. Also, we suggest that CCT mediates the folding of Nsp12 and its assembly into the SARS-CoV-2 RdRp complex, thereby contributing to the replication the SARS-CoV-2 virus. In addition, we present the structure of Nsp12 bound to CCT which reveals their interactions at the the molecular level and shows how CCT contributes to the folding of Nsp12.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Chemistry and Biochemistry

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2023-08-16

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd13345

Keywords

Chaperones, CCT, G protein signaling, SARS-CoV-2

Language

english

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