PAN undergoes structural transitions in response to nucleotide binding, hydrolysis, and release. A, side view of PAN in the absence of nucleotides (left panel) in the presence of ATPγS (middle panel) and when incubated with ADP (right panel). B, the central slice of the three-dimensional structure of PAN in the absence of nucleotides (left panel), in the presence of ATPγS (middle panel), and when incubated with ADP (right panel). The volume of the internal chamber decreases upon nucleotide hydrolysis and release. C, the transition in the orientation of the spikes upon nucleotide hydrolysis and release is illustrated by top view projections of the different nucleotide states of the PAN complex.