K+ is an indispensable cofactor for GrpE stimulation of ATPase activity of DnaK·DnaJ complex from Thermus thermophilus

AbstractK+ is an indispensable cofactor for ATPase activity of eukaryotic cytosolic Hsp70 chaperone systems which lack a GrpE homolog. In the case of the bacterial Hsp70 (DnaK) system, GrpE, a nucleotide exchange factor, stimulates ATPase activity but little is known about the effect of K+. Here, we have cloned a grpE gene from a thermophile, Thermus thermophilus, and purified a homodimeric GrpE protein. Using proteins of this bacterium, we found that the GrpE stimulation of ATPase activity of DnaK·DnaJ complex was absolutely dependent on the presence of K+

Universal description of viscoelasticity with foliation preserving diffeomorphisms

A universal description is proposed for generic viscoelastic systems with a single relaxation time. Foliation preserving diffeomorphisms are introduced as an underlying symmetry which naturally interpolates between the two extreme limits of elasticity and fluidity. The symmetry is found to be powerful enough to determine the dynamics in the first order of strains.Comment: 12 pages, 6 figures, v2:minor changes, v3:clarification adde