Complex interactions between the chaperonin 60 molecular chaperone and dihydrofolate reductase
| Autor: | Paul V. Viitanen, Gail K. Donaldson, Anthony A. Gatenby, George H. Lorimer, Thomas H. Lubben |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
GroES Protein
Macromolecular Substances Protein Conformation Biochemistry Chaperonin Mice Adenosine Triphosphate Bacterial Proteins ATP hydrolysis Enzyme Stability Dihydrofolate reductase Escherichia coli Animals Heat-Shock Proteins biology Chaperonin 60 GroES GroEL Enzyme Activation Tetrahydrofolate Dehydrogenase enzymes and coenzymes (carbohydrates) Chaperone (protein) biology.protein Folic Acid Antagonists Protein folding |
| Zdroj: | Biochemistry. 30:9716-9723 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi00104a021 |
| Popis: | The spontaneous refolding of chemically denatured dihydrofolate reductase (DHFR) is completely arrested by chaperonin 60 (GroEL). This inhibition presumably results from the formation of a stable complex between chaperonin 60 and one or more intermediates in the folding pathway. While sequestered on chaperonin 60, DHFR is considerably more sensitive to proteolysis, suggesting a nonnative structure. Bound DHFR can be released from chaperonin 60 with ATP, and although chaperonin 10 (GroES) is not obligatory, it does potentiate the maximum effect of ATP. Hydrolysis of ATP is also not required for DHFR release since certain nonhydrolyzable analogues are capable of partial discharge. "Native" DHFR can also form a stable complex with chaperonin 60. However, in this case, complex formation is not instantaneous and can be prevented by the presence of DHFR substrates. This suggests that native DHFR exists in equilibrium with at least one conformer which is recognizable by chaperonin 60. Binding studies with 3SS-labeled DHFR support these conclusions and further demonstrate that DHFR competes for a common saturable site with another protein (ribulose-l,5-bisphosphate carboxylase) known to interact with chaperonin 60. Numerous in vitro studies on the folding pathways of chemically denatured proteins have demonstrated that many proteins successfully achieve their correct native structures by using information contained in the primary amino acid se- quence (reviewed by Creighton (1990) and Jaenicke (1987)l. This has led to the general view that protein folding in vivo is also a spontaneous event. However, the cellular reality, for some proteins at least, may be quite different. In part this is due to a temporal element, whereby nascent polypeptides emerge from ribosomes in a vectorial fashion and are subject to the initiation of folding in the absence of the completed chain. A similar situation likely pertains to polypeptides which are translocated across biological membranes. To this must be added the chemical complexity of the cell, in which high concentrations of proteins in various states of folding, and with potentially interactive surfaces, must surely coexist. A class of proteins termed chaperonins (Hemmingsen et al., 1988) have been identified that affect the folding and subsequent assembly of proteins either |
| Databáze: | OpenAIRE |
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