The Janus Face of the Archaeal Cdc48/p97 Homologue VAT: Protein Folding versus Unfolding
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Ralph Golbik
Abstract
Members of the AAA family of ATPases have been implicated in chaperone-like activities. We used the archaeal Cdc48/p97 homologue VAT as a model system to investigate the effect of an AAA protein on the folding and unfolding of two well-studied, heterologous substrates, cyclophilin and penicillinase. We found that, depending on the Mg2+ concentration, VAT assumes two states with maximum rates of ATP hydrolysis that differ by an order of magnitude. In the low-activity state, VAT accelerated the refolding of penicillinase, whereas in the high-activity state, it accelerated its unfolding. Both reactions were ATP-dependent. In its interaction with cyclophilin, VAT was ATP-independent and only promoted refolding. The N-terminal domain of VAT, which lacks ATPase activity, also accelerated the refolding of cyclophilin but showed no effect on penicillinase. VAT appears to be structurally equivalent over its entire length to Sec18/NSF, suggesting that these results apply more broadly to group II AAA proteins.
Copyright © 1999 by Walter de Gruyter GmbH & Co. KG
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- Execution of Apoptosis: Converging or Diverging Pathways?
- Two Highly Related Homeodomain Proteins, Nkx5-1 and Nkx5-2, Display Different DNA Binding Specificities
- The Janus Face of the Archaeal Cdc48/p97 Homologue VAT: Protein Folding versus Unfolding
- Functional Characterization of an Extremely Thermophilic ATPase in Membranes of the Crenarchaeon Acidianus ambivalens
- On the Lysosomal Degradation of Neurofibromin and Its Phosphorylation in Cultured Melanocytes
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- Catalase-Peroxidase from the Cyanobacterium Synechocystis PCC 6803: Cloning, Overexpression in Escherichia coli, and Kinetic Characterization
- Expression of Plasma Prekallikrein mRNA in Human Nonhepatic Tissues and Cell Lineages Suggests Special Local Functions of the Enzyme
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- The Role of Protein Phosphatase 2A Catalytic Subunit Cα in Embryogenesis: Evidence from Sequence Analysis and Localization Studies
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