Doing the right things

Likelihood-based molecular-replacement solution for a highly pathological crystal with tetartohedral twinning and sevenfold translational noncrystallographic symmetry

With the implementation of a molecular-replacement likelihood target that accounts for translational noncrystallographic symmetry, it became possible to solve the crystal structure of a protein with seven tetrameric assemblies arrayed translationally along the c axis. The new algorithm found 56 protein molecules in reduced symmetry (P1), which was used to resolve space-group ambiguity caused by severe twinning.

Structure of a proteolytically resistant analogue of (NLys)⁵SFTI-1 in complex with trypsin: evidence for the direct participation of the Ser214 carbonyl group in serine protease-mediated proteolysis

The structure of a peptide–peptoid analogue inhibitor was determined by X-ray crystallography. It is the first structure to reveal the structural basis of the complete proteolytic resistance towards serine proteases by inhibitors containing a peptoid residue at the P1 position.

Na⁺/K⁺ exchange switches the catalytic apparatus of potassium-dependent plant L-asparaginase

Three crystal structures of potassium-dependent plant L-asparaginase were solved in complexes with K⁺, with Na⁺ and with both cations. A novel alkali metal-binding loop Val111–Ser118 (the activation loop) changes its conformation upon K⁺/Na⁺ exchange, leading to a reconfiguration of three key residues, His117, Arg224 and Glu250 (the catalytic switch), to allow or prevent substrate binding in the active site of the enzyme.

Specific binding of gibberellic acid by Cytokinin-Specific Binding Proteins: a new aspect of plant hormone-binding proteins with the PR-10 fold

Two plant cytokinin-specific binding proteins were crystallized in complex with gibberellic acid (GA3), which is an entirely different plant hormone. The crystal structures, determined at high resolution, reveal a highly specific mode of GA3 binding, calling for a revision of the hormone specificity of plant proteins with the PR-10 fold.