issue contents

Journal logoSTRUCTURAL
ISSN: 2059-7983

April 2017 issue

Highlighted illustration

Cover illustration: Hfq is a bacterial Sm protein that regulates mRNA expression and turnover, largely by facilitating the annealing of small noncoding RNAs and their mRNA targets. Two crystal structures of an Hfq homolog from the ancient bacterium Aquifex aeolicus have been determined to 1.5 Å resolution, one in apo form and the other with RNA bound (Stanek et al., p. 294). In the apo form, Hfq crystallized as two hexameric rings stacked in a head-to-tail orientation; as can be seen in this axial view of the dodecamer, the rings are not in perfect rotational register. In this ribbon diagram, the top hexamer is coloured blue and cyan, and Hfq subunits in the bottom hexamer are alternatingly yellow and orange. Molecules of MPD (grey carbons) and GndCl (green carbons) are shown as ball-and-stick representations, and Cl- ions are yellow spheres. The Gnd cations and Cl- anions form a `salty' layer at the ring interface (transverse view in Fig. 5b of the text).

research papers

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A multidimensional scaling analysis of pairwise correlation coefficients is presented which positions data sets in a sphere with unit radius of an abstract, low-dimensional space at radii inversely proportional to their levels of random error and at spherical angles related to their mutual systematic differences. This reduction in dimensionality can not only be used for classification purposes, but also to derive data-set relations on a continuous scale.

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The structure of an Hfq homolog from the deep-branching thermophilic bacterium Aquifex aeolicus, determined to 1.5 Å resolution both in the apo form and bound to a uridine-rich RNA, reveals a conserved, pre-organized RNA-binding pocket on the lateral rim of the Hfq hexamer.

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Using all available metal-containing organic compound structures in the Cambridge Structural Database, a novel data-driven method to derive bond-valence R0 parameters was developed. While confirming almost all reference literature values, two distinct populations of FeII—N and FeIII—N bonds are observed, which are interpreted as low-spin and high-spin states of the coordinating iron. Based on the R0 parameters derived here, guidelines for the modeling of iron–ligand distances in macromolecular structures are suggested.

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This study of shrimp thioredoxin sheds new light on the existence of monomeric and dimeric populations in solution. It is demonstrated that the Cys73 residue is essential for dimer formation and that the Cys73Ser mutant has the same activity as the wild type.

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In eight of the nine crystal structures of M. smegmatis MutT1 reported here, an arrangement is observed in which domain 1 of one molecule and domain 2 of a neighbouring molecule (trans domain 2) are brought into close proximity, with ligand-binding sites at the interface between the two domains. This and other structural observations, along with biochemical results, lead to a plausible proposal for the mechanism of action of the enzyme.

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The crystal structures of Hsp104 N-terminal domains from S. cerevisiae (ScHsp104NTD) and C. albicans (CaHsp104NTD) were determined to high resolution. The structures of ScHsp104NTD and CaHsp104NTD reveal that the yeast Hsp104 N-terminal domain may utilize a conserved putative peptide-binding groove to interact with misfolded polypeptides.

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A time- and sample-efficient approach for the serial collection of room-temperature diffraction data using a fixed target at a synchrotron is demonstrated.

letters to the editor

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The term `atomic resolution' is very often abused in presenting macromolecular structures.

book reviews

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