Crystal structures of DENV NS2B-NS3pro and overview of PCSs measured versus the amino acid sequence.

<p>(A) Open state as observed in the ligand-free conformation in the crystal structure 2FOM [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref026" target="_blank">26</a>]. NS2B is shown in green and NS3pro is shown in grey. The orange balls identify the locations of residues 34 and 68. We refer to the mutants S34C and S68C as mutants B and C, respectively [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref023" target="_blank">23</a>]. To induce PCSs in the protein, the mutants B and C were reacted with a single lanthanide binding tag to form a disulfide bond with either of the cysteine residues at these sites. (B) Closed state as observed in the crystal structure 3U1I [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref022" target="_blank">22</a>] with the same color coding as in (A). The closed conformation is presumed to represent the enzymatically active state. (C) Summary of the experimental PCSs. C1 and C2 denote two different lanthanide binding tags used. They differ only in chirality [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref023" target="_blank">23</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref028" target="_blank">28</a>]. Open circles, filled circles, and boxes identify the residues for which PCSs were observed with Tb³⁺, Tm³⁺, or both Tb³⁺ and Tm³⁺, respectively. The residue numbering used is shown at the top of the amino acid sequence. In this numbering scheme, the mutants B and C are at residues 94 and 129 (highlighted in orange). The green and grey characters identify, respectively, the NS2B and NS3pro segments for which coordinates are reported in the crystal structures (PDB ID: 2FOM, 3U1I). Sequence segments for which no electron density was observed, are highlighted in blue. These parts are probably flexible [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref025" target="_blank">25</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127053#pone.0127053.ref027" target="_blank">27</a>].