Diffraction cartography: applying microbeams to macromolecular crystallography sample evaluation and data collection

New tools for the evaluation of the diffraction characteristics of crystals of macromolecules are presented in the context of the ESRF Upgrade MASSIF beamlines.

Structure of the N-terminal fragment of Escherichia coli Lon protease

The medium-resolution structure of the N-terminal fragment of E. coli Lon protease shows that this part of the enzyme consists of two compact domains and a very long α-helix.

The first crystal structure of a gramicidin complex with sodium: high-resolution study of a nonstoichiometric gramicidin D–NaI complex

The crystal structure of the nonstoichiometric complex of gramicidin D with NaI has been studied using synchrotron radiation at 100 K.

Structure of Staphylococcus aureus adenylo­succinate lyase (PurB) and assessment of its potential as a target for structure-based inhibitor discovery

The 2.5 Å resolution structure of S. aureus adenylosuccinate lyase is reported and compared with those of orthologues to assess its potential as a template for early stage drug discovery. AMP and a putative assignment of oxalate, the latter an artefact possibly arising from an impurity in the PEG used for crystallization, occupy the active site.

Validation of crystallographic models containing TLS or other descriptions of anisotropy

Guidelines and specific tests for validating macromolecular crystal structures that include TLS models are introduced. Validation may used to troubleshoot problems during refinement, to confirm the internal consistency of the model as part of deposition into the Protein Data Bank or to assess the plausibility of interpretating the boundary between two TLS groups as indicating a hinge point between structural domains.

Qu­antitive evaluation of macromolecular crystallization experiments using 1,8-ANS fluorescence

A novel approach is presented for the visualization of crystallization experiments using fluorescence from trace amounts of a nonspecific dye.

Structural and functional analysis of Rv0554 from Mycobacterium tuberculosis: testing a putative role in mena­quinone biosynthesis

The crystal structure of Rv0554 from M. tuberculosis has been determined, revealing a dimeric protein with an α/β-hydrolase fold. Functional assays failed to support a proposed role in menaquinone biosynthesis.

Structural basis of the histidine-mediated vitamin D receptor agonistic and antagonistic mechanisms of (23S)-25-de­hydro-1α-hydroxyvitamin D₃-26,23-lactone

The molecular mechanism of the VDR-antagonistic action of TEI-9647 is investigated.

Promoting crystallization of antibody–antigen complexes via microseed matrix screening

The application of microseed matrix screening to the crystallization of related antibodies in complex with IL-13 is described. Both self-seeding or cross-seeding helped promote nucleation and increase the hit rate.

Crystallographic binding studies with an engineered monomeric variant of triosephosphate isomerase

Crystallographic binding studies of a monomeric variant of triosephosphate isomerase (A-TIM) with a modified more extended binding pocket between loop-7 and loop-8 are reported. Wild-type TIM exclusively catalyses the isomerization of the C3-sugar phosphates dihydroxyacetonephosphate and D-glyceraldehyde-3-phosphate. These crystallographic studies show that the new binding pocket of A-TIM can also bind analogues of C4-sugar phosphates and C5-sugar phosphates.

Enhancing MAD F_A data for substructure determination

A new statistical and computational procedure, which merges multiple F_A estimates into an averaged data set, is used to further improve the quality of the estimated anomalous amplitudes for substructure determination.

Emerging from pseudo-symmetry: the redetermination of human carbonic anhydrase II in monoclinic P2₁ with a doubled a axis

The structure of human carbonic anhydrase II in the monoclinic P2₁ space group with a doubled a axis from that of the usually observed unit cell has been re-determined and shown that the choice for how the four molecules in the unit cell are grouped (based on their coordinates) into pairs that represent a single asymmetric unit determines whether or not rotational disorder is observed/created during refinement.