Biomaterial Database

Trigonal DnaK-DnaJ complex versus free DnaK and DnaJ: heat stress converts the former to the latter, and only the latter can do disaggregation in cooperation with ClpB. 2004

Yo-Hei Watanabe, and Masasuke Yoshida

Chemical Resources Laboratory, R-1, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503, Japan.

DnaK from Thermus thermophilus (TDnaK) is unique because significant fractions of cellular TDnaK exist as a trigonal K.J complex that consists of three copies each of TDnaK, TDnaJ, and an assembly factor TDafA. Here, chaperone functions of the K.J complex and free TDnaK plus free TDnaJ (K+J) were compared. Substrate proteins were completely denatured at 72-73 degrees C or 89 degrees C in the absence or the presence of K.J complex or K+J and were subsequently incubated at a moderate temperature of 55 degrees C. TGrpE and ATP were always included in the K.J complex and K+J, and TClpB was supplemented at 55 degrees C. At 72-73 degrees C, both the K.J complex and K+J suppressed heat aggregation of substrate proteins. During the next incubation at 55 degrees C, K+J, assisted by TClpB, was able to disaggregate the heat aggregates and efficiently reactivate activities of the proteins, whereas the K.J complex was not; it reactivated only the soluble inactivated proteins. When substrate proteins were heated to 89 degrees C, both the K.J complex and K+J were no longer able to prevent heat aggregation, and because of selective, irreversible denaturation of TDafA the K.J complex dissociated into K+J, which then exhibited disaggregation activity during the next incubation at 55 degrees C. Thus, TClpB-assisted disaggregation activity belongs only to K+J, and TDafA is a potential thermosensor for converting the K.J complex to K+J in response to heat stress.

UI	MeSH Term	Description	Entries
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011489	Protein Denaturation	Disruption of the non-covalent bonds and/or disulfide bonds responsible for maintaining the three-dimensional shape and activity of the native protein.	Denaturation, Protein,Denaturations, Protein,Protein Denaturations
D006358	Hot Temperature	Presence of warmth or heat or a temperature notably higher than an accustomed norm.	Heat,Hot Temperatures,Temperature, Hot,Temperatures, Hot
D006360	Heat-Shock Proteins	Proteins which are synthesized in eukaryotic organisms and bacteria in response to hyperthermia and other environmental stresses. They increase thermal tolerance and perform functions essential to cell survival under these conditions.	Stress Protein,Stress Proteins,Heat-Shock Protein,Heat Shock Protein,Heat Shock Proteins,Protein, Stress
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D015964	Gene Expression Regulation, Bacterial	Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.	Bacterial Gene Expression Regulation,Regulation of Gene Expression, Bacterial,Regulation, Gene Expression, Bacterial
D016963	Thermus thermophilus	A species of gram-negative, aerobic, rod-shaped bacteria found in hot springs of neutral to alkaline pH, as well as in hot-water heaters.
D017510	Protein Folding	Processes involved in the formation of TERTIARY PROTEIN STRUCTURE.	Protein Folding, Globular,Folding, Globular Protein,Folding, Protein,Foldings, Globular Protein,Foldings, Protein,Globular Protein Folding,Globular Protein Foldings,Protein Foldings,Protein Foldings, Globular
D018832	Molecular Chaperones	A family of cellular proteins that mediate the correct assembly or disassembly of polypeptides and their associated ligands. Although they take part in the assembly process, molecular chaperones are not components of the final structures.	Chaperones, Molecular,Chaperone, Molecular,Molecular Chaperone
D020673	Protein Renaturation	The reconstitution of a protein's activity following denaturation.	Renaturation, Protein,Protein Renaturations,Renaturations, Protein