FIGURE 1.

Structure of AtClpS1. (a) Structure of the AtClpS1‐peptide complex. Secondary structures are labeled in numerical order. N‐ and C‐termini are indicated as Nt and Ct, respectively, with the residue number in parentheses, and the ribbon color changes from blue (Nt) to red (Ct) gradually. The bound N‐degron (Phe‐Ala) is shown in the stick model. (b) Transparent molecular surface with electrostatic potentials shows the distribution of positively and negatively charged surfaces, colored blue and red, respectively. The entrance of the N‐degron binding pocket possesses positively charged residues, which are known as the gatekeeper. (c) Sequence alignment of ClpS structures in the Protein Data Bank (3o2b: Escherichia coli ClpS; 3gw1: Caulobacter crescentus ClpS; 4o2x: Plasmodium falciparum ClpS; and 4yjm: Agrobacterium tumefaciens ClpS2). The characteristic shortened helix in the eukaryotic ClpS proteins is boxed in red. (d) Comparison of the overall structure of AtClpS1 with structures of other ClpS proteins. The calculated root‐mean‐square deviation (RMSD) values between AtClpS1 and other ClpS proteins were 1.316 Å (EcClpS; 79 matching Cα atoms), 1.102 Å (CcClpS; 75 matching Cα atoms), 0.961 Å (PfClpS; 73 matching Cα atoms), and 1.413 Å (AtuClpS2; 77 matching Cα atoms). The red boxes represent the shortened α3‐helix, which is the most structurally divergent region