Introduction to the virtual thematic issue on room-temperature biological crystallography

Room-temperature biological crystallography has seen a resurgence in recent years and a collection of articles recently published in IUCrJ, Acta Cryst. D Structural Biology and Acta Cryst. F Structural Biology Communications, have been collected together to produce a virtual special issue at https://journals.iucr.org/special_issues/2022/RT/.

Likelihood-based signal and noise analysis for docking of models into cryo-EM maps

Likelihood-based rotation, translation and refinement targets have been derived for docking models into cryo-EM reconstructions.

Likelihood-based docking of models into cryo-EM maps

Exploiting analogies to crystallographic molecular replacement, a strategy for docking into cryo-EM maps is informed by the calculation of expected log-likelihood-gain scores.

Ambient temperature structure of phosphoketolase from Bifidobacterium longum determined by serial femtosecond X-ray crystallography

Ambient temperature structures of B. longum phosphoketolase holoenzyme and its complex with a putative inhibitor, phosphoenolpyruvate, demonstrated striking conformational change of the loop at the entrance to the active-site pocket compared with known cryogenic temperature phosphoketolase structures. This structural change highlighted the reaction mechanism and substrate specificity of this enzyme.

Conformation-dependent ligand hot spots in the spliceosomal RNA helicase BRR2

Fragment derivatives occupy diverse binding sites in two crystal forms of the RNA helicase BRR2 that coincide with predicted, conformation-dependent ligand hot spots.

Structures of L-proline trans-hydroxylase reveal the catalytic specificity and provide deeper insight into AKG-dependent hydroxylation

L-Proline trans-hydroxylase and its complexes with substrate and product reveal the structural basis of trans–cis proline hydroxylation selectivity. Structure-based sequence alignment and structural comparison suggest signatures for in-line or off-line AKG-binding modes in AKG-dependent hydroxylases and provide deeper insight into AKG-dependent hydroxylation.

Buccaneer model building with neural network fragment selection

A neural network trained to identify unfavourable fragments and therefore improve protein model building in the Buccaneer software is described.

Multivariate estimation of substructure amplitudes for a single-wavelength anomalous diffraction experiment

A new equation for the calculation of substructure-factor amplitudes for substructure detection from a single-wavelength anomalous diffraction experiment produces better results compared with the currently used estimates in test cases.

The structure of the complex between the arsenite oxidase from Pseudorhizobium banfieldiae sp. strain NT-26 and its native electron acceptor cytochrome c₅₅₂

The crystal structure of the electron transfer complex between arsenite oxidase (AioAB) from Pseudorhizobium banfieldiae sp. strain NT-26 and its native electron acceptor cytochrome c₅₅₂ (cytc₅₅₂) is presented. Cytc₅₅₂ docks within a cleft at the interface of the AioA and AioB subunits, which allows a close association between redox cofactors.; this close association presumably facilitates fast electron transfer and underpins the ability of this organism to respire in arsenic contaminated environments.

The X-ray crystallography phase problem solved thanks to AlphaFold and RoseTTAFold models: a case-study report. Corrigendum

The article by Barbarin-Bocahu & Graille [(2022), Acta Cryst. D78, 517–531] is corrected.