Structure and conformational plasticity of the U6 small nuclear ribonucleoprotein core

A crystal structure of the U6 snRNP core from yeast shows that mutation of the U6 internal stem-loop (ISL) does not alter the overall topology of the snRNP, but suggests structural plasticity in the ISL.

Structural studies of substrate and product complexes of 5-aminolaevulinic acid dehydratase from humans, Escherichia coli and the hyperthermophile Pyrobaculum calidifontis

X-ray structures of the enzyme 5-aminolaevulinate dehydratase (ALAD) purified from human blood, as well as the recombinant human form and the ALAD from the hyperthermophilic archaeon P. calidifontis, are reported, together with the structure of E. coli ALAD co-crystallized with a noncovalently bound moiety of the product, porphobilinogen. The structures give insight into the zinc-dependence of these enzymes, the possible role of electrostatics in substrate funnelling and details of the interactions made by the bound pyrrole end product.

Solution of the structure of a calmodulin–peptide complex in a novel configuration from a variably twinned data set

A description is given of the structure solution of a nearly perfectly hemihedrally twinned novel calmodulin–peptide complex by molecular replacement in combination with single-wavelength anomalous diffraction. The resulting structure revealed a unique mode of peptide–calmodulin interaction in which the peptide is bent to nearly 90° within the calmodulin-binding pocket.

The structure of a calcium-dependent phosphoinositide-specific phospholipase C from Pseudomonas sp. 62186, the first from a Gram-negative bacterium

The structure of the calcium-dependent phosphoinositide-specific phospholipase C from Pseudomonas sp. 62186 is described, the first from a Gram-negative bacterium. Structure solution from a low-sequence-identity homology model is described in detail.

Q|R: quantum-based refinement

Quantum-based refinement software is being developed to refine biomacromolecules against crystallographic or cryo-electron microscopy data.

Crystal structure of human chondroadherin: solving a difficult molecular-replacement problem using de novo models

The structure of human chondroadherin (hCHAD), a 359-amino-acid protein with 11 leucine-rich repeats, has been solved by molecular replacement using de novo models of a 195-residue segment and the AMPLE pipeline. This demonstrates that even a fairly large β-rich protein is tractable to solution using de novo modelling. The structure of the C-terminal domain of hCHAD reveals the conformation of a medically relevant peptide.

Learning from oligosaccharide soaks of crystals of an AA13 lytic polysaccharide monooxygenase: crystal packing, ligand binding and active-site disorder

In the course of soaking experiments of lytic polysaccharide monooxygenase crystals with potential oligosaccharide ligands, local changes in crystal packing, various degrees of active-site disorder and binding of oligosaccharides at potential branching or surface binding sites were observed.