issue contents
January 2011 issue
Cover illustration: Multi-crystal SAD phasing of a relatively large structure (1456 ordered residues) at relatively low resolution (3.5 Å) (p. 45). Statistical measures of data quality are plotted as a function of the number of crystals (blue figures across the abscissa) used in the mergers of data: anomalous correlation coefficient (red), F/(F) (green), map correlation coefficient (orange), CCweak (blue) and I/(I) (purple). Ordinate scales and origins are arbitrary; actual values are in Table 3 and 6 of the article. The background shows a ribbon diagram (drawn by PyMOL) for the contents of one asymmetric unit: two sensor domains of a histidine kinase receptor from the human gut symbiont Bacteroides thetaiotaomicron.
research papers
These data reveal that the ethyl esters of a series of 5′-(ω-carboxyalkoxy)benzylpyrido[2,3-d]pyrimidines have flexible side-chain conformations that do not optimize interactions with Arg75 in pcDHFR. Also, a novel conformation not reported in other DHFR structures was observed for one conformer of one of the compounds that had a disordered side chain.
PDB references: pcDHFR–1, 3nz6; pcDHFR–2, 3nz9; pcDHFR–3, 3nza; pcDHFR–4, 3nzb; pcDHFR–5, 3nzc; hDHFR–3, 3nzd
The successful incorporation of SeCys and SeMet into a recombinant protein, yielding derivatized crystals suitable for phasing, is reported. This is the first report of such double derivatization using non-auxotrophic E. coli strains and where SeCys SAD was sufficient for phasing with no contribution from substituted methionine.
PDB reference: CsgC, 2xsk
The crystal structure of a human PP2A methyltransferase enzyme has been determined at 2.0 Å resolution. The structure provides a foundation for the development of specific inhibitors of PP2A methylation, which regulates PP2A holoenzyme assembly.
PDB reference: leucine carboxyl methyltransferase 1, 3o7w
A 2.7 Å resolution crystal structure of the catalytic domain of map kinase phosphatase 4 (MKP-4C) is presented.
PDB reference: catalytic domain of MKP-4, 3lj8
Selenomethionine-derivatized protein crystals undergo site-specific ultraviolet laser-induced radiation damage, which was successfully exploited for radiation-damage-induced phasing of X-ray diffraction data.
Anomalous diffraction signals can be very weak and sensitive to radiation damage. Here, in application to a poorly diffracting (dmin of 3.5 Å) and relatively large structure (1456 ordered residues), it is shown that data merged from multiple crystals can support SAD structure determination when no single data set is adequate.
A new crystal form of the R163K variant of human thymidylate synthase (hTS) with five subunits per asymmetric part of the unit cell, all with loop 181–197 in the active conformation, is reported.
The structures of SgrAI bound to secondary-site DNA and Ca2+ or Mg2+, as well as bound to cleaved primary-site DNA and Mg2+, are presented and show similar overall conformations interpreted as the low-activity form of the enzyme. A third Mg2+ ion-binding site is found in the structure with cleaved primary-site DNA, as predicted by the two-metal-ion mechanism.
international union of crystallography
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