Topical Reviews in Acta Crystallographica F Structural Biology Communications

Editors of Acta Cryst. F Structural Biology Communications discuss their plans for topical reviews.

Finding order in chaos – nanocrystals in amorphous protein gels

Measurements of protein dense phases reveal the presence of highly ordered protein nanostructures. Such phases may be candidates for structural biology measurements on next-generation instruments for molecules that are difficult or impossible to crystallize.

The crystal structures of the enzyme hydroxymethylbilane synthase, also known as porphobilinogen deaminase

Thirty years of crystal structures of the enzyme hydroxymethylbilane synthase are surveyed in this topical review. These crystal structures aim at the elucidation of the structural basis of the complex reaction mechanism involving the formation of tetrapyrrole from individual porphobilinogen units.

Crystal structure of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis

Acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis (TTE0866) catalyzes the deacetylation of cellulose acetate. The crystal structure of TTE0866 at 1.9 Å resolution revealed the catalytic domain, but electron density was not observed for the N-terminal region. The active-site conformation of TTE0866 was similar to those of other carbohydrate esterase family 4 enzymes, but the orientation of the Trp264 side chain was distinct, which may contribute to its reactivity towards highly substituted cellulose acetate.

Crystal structure of the [2Fe–2S] protein I (Shethna protein I) from Azotobacter vinelandii

Several Azotobacter iron–sulfur proteins probably play roles in the complex redox chemistry that Azotobacter must maintain when fixing nitrogen. The 2.1 Å resolution crystal structure of the [2Fe–2S] protein I (Shethna protein I) from Azotobacter vinelandii reveals a homodimer similar to the structure of the thioredoxin-like [2Fe–2S] protein from Aquifex aeolicus, with the [2Fe–2S] cluster coordinated by the surrounding conserved cysteine residues.

Nanocrystalline protein domains via salting-out

Microstructural measurements of salted-out protein dense phases show that they contain highly ordered protein nanostructures that assemble hierarchically to create the phase. Such phases may be candidates for structural biology measurements on next-generation instruments for molecules that are difficult or impossible to crystallize in bulk.

Crystal structures of glycogen-debranching enzyme mutants in complex with oligosaccharides

Five crystal structures of glycogen-debranching enzyme mutants in complex with oligosaccharides are reported.

Crystal structure of N-terminal degron-truncated human glutamine synthetase

The crystal structure of N-terminal degron-truncated human glutamine synthetase was determined at 2.95 Å resolution, which revealed that the N-degron is not essential for decamer formation. The study also investigated the roles of N-degron in oligomerization and enzymatic activities through biochemical analyses.