The Modeling of GroEL to Understand its Function
Authors: Grover Sahiba , Kandru Namratha , Razo Julissa , Mendoza Naomi , Kenana Jaida , Dvoretz Illay 
Published: November 2023

Proteins are vital to the function of organisms; however, they are metastable and highly susceptible to denaturation. As protein synthesis requires extensive amounts of energy, chaperonins renature malformed proteins to conserve resources. In E coli, chaperonins called GroEL (Large) and GroES (Small) possess a variety of conformational states that help fold, refold, or actively maintain proteins in their functional form. A physical model of GroEL was constructed to understand how it interacts with denatured proteins in order to refold them. GroEL is composed of two 57 kDa heptameric subunits, stacked back to back. These subunits possess three domains: the apical, intermediate, and equatorial domains. The apical domain binds partially folded proteins and, in the presence of ATP or ADP, binds to GroES. In the absence of GroES, the apical domains interact and form a seven membered ring that contains a rim of hydrophobic amino acids, which comprise the binding region. The intermediate domain connects the apical and equatorial domains and communicates binding energies to facilitate movement of the apical domain. The equatorial domain binds to ATP to induce a conformational change in GroEL, which buries the once exposed hydrophobic residues, resulting in a decreased binding of the denatured protein to the chaperonin. The bound protein substrate is then released into a large, hydrophilic internal cavity, which is caused by the GroEL‐GroES complex formation. This cavity allows for individual proteins to fold and avoid aggregation when ATP binds and prevents premature release of partially folded proteins into the cytosol. Chaperonin facilitated folding begins with the binding of hydrophobic, non‐native substrate proteins onto the apical domain. ATP then binds to the equatorial domain of a protein loaded ring and induces a conformational change in the GroEL apical domain. GroES then binds to the apical domain, releasing the substrate into the GroEL‐GroES cavity, resulting in a cis conformation. As ATP is hydrolyzed in the cis ring, another partially folded protein and more ATP molecules bind to the unoccupied trans GroEL ring. This second non‐native protein/ATP binding event induces the release of the cis bound GroES from the complex, releasing the protein back into the E. coli cytosol. Chaperonins like GroEL are vital to folding proteins in E coli, and deleterious mutations in these proteins or even diminished levels of them in E coli are lethal. This is a SMART team project supported by the Milwaukee School of Engineering. The Olathe North CBM SMART Team used 3‐D modeling and printing technology to examine structure‐function relationships of GrowEL.

Support or Funding Information

Olathe North High School SMART Team I. Dvoretz, S. Grover, N. Kandru, J. Kenana, N. Mendoza, J. Razo Teachers: C. Elniff, L.B. Fogt Mentor: Dr. Mark Fisher, Department of Biochemistry and Molecular Biology, University of Kansas Medical Center PDB: 1AON Primary Citation: Mark T. Fisher. (1992) Promotion of the in Vitro Renaturation of Dodecameric Glutamine Synthetase from Escherichia coli in the Presence of GroEL (Chaperonin‐60) and ATP. Biochemistry 1992. 31: 3955–3963 Project supported by Olathe North Life Sciences and the Milwaukee School of Engineering.