Cover picture: Mutations (E22K:H104R) of human PNP, remote from the catalytic site, alter active site dynamics and influence catalytic properties. The yellow arrows indicate the vector of conformational perturbation from H104R-mutated residue of subunit C to the active site of subunit A (site of Immucillin-G transition state inhibitor binding). The side chain of Arg-104^C perturbs the motion of the Phe-159^C loop to increase its mobility, represented by the color-spectrum of backbone fluctuation (blue to red color spectrum represents most rigid to most flexible, respectively). See the article by Saen-Oon et al. on page 4078.