Fig. 2: The hClpX E-loop senses nucleotide states and facilitates inter-subunit communication.
From: Cryo-EM structures of human ClpXP reveal mechanisms of assembly and proteolytic activation
a The hClpX hexamer is shown as a surface representation, highlighting the E-loop (shown as licorice/ovals style) of one hClpX subunit extends away to interact with the neighboring subunit. The inset illustrates the network of interactions between the E-loop of chain E and chain D, emphasizing that E285 from chain E is within hydrogen bonding distance of the ATP nucleotide. b NADH/ATP-coupled ATPase assays were performed. The negative controls include reactions without enzymes and the Walker B mutant—hClpXE395A. Removal of the E-loop from hClpX caused a 2-fold decrease in hClpX ATPase activity. The E285A mutation has a similar deleterious effect on hClpX ATPase activity as the E-loop deletion. Data are presented as bar graphs showing mean values with error bars representing standard deviation from three independent replicates. c Removal of the E-loop from hClpX or introduction of the E285A mutation resulted in a 10X reduction in the FITC-casein degradation activity of the hClpXP complex. Data are presented as bar graphs showing mean values with error bars showing standard deviation from three independent replicates. Source data are provided as a Source Data file.
