ClpB cooperates with the DnaK chaperone system in the reactivation of protein from aggregates and is a member of the ATPases associated with a variety of cellular activities (AAA+) protein family. The underlying disaggregation reaction is dependent on ATP hydrolysis at both AAA cassettes of ClpB but the role of each AAA cassette in the reaction cycle is largely unknown. Here we analyze the activity of the separately expressed and purified nucleotide binding domains of ClpB from Thermus thermophilus. The two fragments show different biochemical properties: the first construct is inactive in ATPase activity assays and binds nucleotides weakly, the second construct has a very high ATPase activity and interacts tightly with nucleotides. Both individual fragments have lost their chaperone function and are not able to form large oligomers. When combined in solution, however, the two fragments form a stable heterodimer with oligomerization capacities equivalent to wild-type ClpB. This non-covalent complex regains activity in reactivating protein aggregates in cooperation with the DnaK chaperone system. Upon complex formation the ATPase activity of fragment 2 is reduced to a level similar to wild-type ClpB. Hence functional ClpB can be reassembled from its isolated AAA cassettes showing that covalent linkage of these domains is not a prerequisite for the chaperone activity. The observation that the intrinsically high ATPase activity of AAA2 is suppressed by AAA1 allows a hypothetical assignment of their mechanistic function. Whereas the energy gained upon ATP hydrolysis at the AAA2 is likely to drive a conformational change of the structure of ClpB, AAA1 might function as a regulator of the chaperone cycle.
Introduction: Protein acetylation is an extensively investigated post-translational modification (PTM). In addition to lysine acetylation, three new types of lysine acylations characterized by the presence of an acidic carboxylic group have been recently identified and validated. These included lysine malonylation (Kmal), lysine succinylation (Ksucc) and lysine glutarylation (Kglu).
In euryhaline teleosts, the cystic fibrosis transmembrane conductance regulator (CFTR) in seawater (SW)-type chloride cells facilitates apical Cl secretion for SW adaptation, while alternative Cl excretion pathways remain understudied. This study investigates the role of the calcium-activated chloride channel, Anoctamin 1 (ANO1), in the gills of the euryhaline Japanese medaka (Oryzias latipes) under hyperosmolality and cortisol (CORT) influence. Acclimation to artificial SW, NaCl, mannitol, or glucose significantly upregulated ANO1 and CFTR mRNA expression in gills, unlike urea treatment.
Oxidative stress-induced DNA damage is an important mechanism that leads to the death of neuronal cells after ischemic stroke. Our previous study found that Ku70 was highly expressed in ischemic brain tissue of rats after cerebral ischemia-reperfusion injury. However, the role of Ku70 in glucose-oxygen deprivation/reperfusion (OGD/R) in astrocytes has not been reported.
The super-relaxed (SRX) state of myosin ATPase activity is critical for striated muscle function, and its dysregulation is linked to cardiomyopathies. It is unclear whether the SRX state exchanges readily with the disordered-relaxed (DRX) state, and whether the SRX state directly corresponds to the folded back interacting-head motif (IHM). Using recombinant β-cardiac heavy meromyosin (HMM) and subfragment 1 (S1), which cannot form the IHM, we show that the SRX and DRX populations are in rapid equilibrium, dependent on myosin head-tail interactions.
The PEX1/PEX6 AAA-ATPase is required for the biogenesis and maintenance of peroxisomes. Mutations in and disrupt peroxisomal matrix protein import and are the leading cause of Peroxisome Biogenesis Disorders (PBDs). The most common disease-causing mutation in PEX1 is the PEX1 allele, which results in a reduction of peroxisomal protein import.
