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Acta Crystallographica Section D

Acta Crystallographica Section D: Biological Crystallography welcomes the submission of articles covering any aspect of structural biology, with a particular emphasis on the structures of biological macromolecules and the methods used to determine them. R

Published: 2017-06-23


1.8 Å resolution crystal structure of the carbapenem intrinsic resistance protein CarF


The natural production of the β-lactam antibiotic carbapenem in bacteria involves a group of enzymes that form a synthetic pathway as well as proteins that protect the cell from self-intoxification by the products. Here, the crystal structure of CarF, one of the two proteins that confer resistance to synthesis of the antibiotic in the host organism, is reported. The CarF fold places it within a widely occurring structural family, indicating an ancient structural origin from which the resistance function has been derived.

DNA conformational transitions inferred from re-evaluation of m|Fo| − D|Fc| electron-density maps


Conformational flexibility of DNA plays important roles in biological processes such as transcriptional regulation and DNA packaging etc. To understand the mechanisms of these processes, it is important to analyse when, where and how DNA shows conformational variations. Recent analyses have indicated that conventional refinement methods do not always provide accurate models of crystallographic heterogeneities and that some information on polymorphism has been overlooked in previous crystallographic studies. In the present study, the m|Fo| − D|Fc| electron-density maps of double-helical DNA crystal structures were calculated at a resolution equal to or better than 1.5 Å and potential conformational transitions were found in 27% of DNA phosphates. Detailed analyses of the m|Fo| − D|Fc| peaks indicated that some of these unassigned densities correspond to ZI ↔ ZII or A/B → BI conformational transitions. A relationship was also found between ZI/ZII transitions and metal coordination in Z-DNA from the detected peaks. The present study highlights that frequent transitions of phosphate backbones occur even in crystals and that some of these transitions are affected by the local molecular environment.