On the chaperonin activity of GroEL at heat-shock temperature

• Published in: The international journal of biochemistry & cell biology 2005-07, Vol.37 (7), p.1375-1385
• Main Authors: Melkani, Girish C., Zardeneta, Gustavo, Mendoza, Jose A.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - chemistry; Chaperone; Chaperonin 60 - chemistry; GroEL complex; Heat shock temperature; Heat-Shock Response; Heating; Protein Binding; Protein Conformation; Protein Denaturation; Protein Folding; Refolding; Rhodanese; Stability; Thiazoles - chemistry; Thiosulfate Sulfurtransferase - chemistry
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2005.01.007

The studies of GroEL, almost exclusively, have been concerned with the function of the chaperonin under non-stress conditions, and little is known about the role of GroEL during heat shock. Being a heat shock protein, GroEL deserves to be studied under heat shock temperature. As a model for heat shock in vitro, we have investigated the interaction of GroEL with the enzyme rhodanese undergoing thermal unfolding at 43 °C. GroEL interacted strongly with the unfolding enzyme forming a binary complex. Active rhodanese (82%) could be recovered by releasing the enzyme from GroEL after the addition of several components, e.g. ATP and the co-chaperonin GroES. After evaluating the stability of the GroEL–rhodanese complex, as a function of the percentage of active rhodanese that could be released from GroEL with time, we found that the complex had a half-life of only one and half-hours at 43 °C; while, it remained stable at 25 °C for more than 2 weeks. Interestingly, the GroEL–rhodanese complex remained intact and only 13% of its ATPase activity was lost during its incubation at 43 °C. Further, rhodanese underwent a conformational change over time while it was bound to GroEL at 43 °C. Overall, our results indicated that the inability to recover active enzyme at 43 °C from the GroEL–rhodanese complex was not due to the disruption of the complex or aggregation of rhodanese, but rather to the partial loss of its ATPase activity and/or to the inability of rhodanese to be released from GroEL due to a conformational change.