Ab initio macromolecular phasing has been so far limited to small proteins diffracting at atomic resolution (beyond 1.2 A) unless heavy atoms are present. We describe a general ab initio phasing method for 2 A data, based on combination of localizing model fragments such as small á-helices with Phaser and density modification with SHELXE. We implemented this approach in the program Arcimboldo to solve a 222-amino-acid structure at 1.95 A.

Three not of a kind: A NMR HNP experiment can distinguish between all three possible single‐ and double‐phosphorylated histidines without requiring pKa or chemical shift information (see picture). The method is tested on phosphorylated histidines and phosphocarrier protein HPr. It detects phosphorylation in phosphotransferase system regulation domain I (PRDI).

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GlcT is a transcriptional antiterminator protein that is involved in regulation of glucose metabolism inBacillus subtilis. Antiterminator proteins bind specific RNA sequences, thus preventing the formation of overlapping terminator stem-loops. The structure of a fragment (residues 3–170) comprising the RNA-binding domain (RBD) and the first regulatory domain (PRDI) of GlcT was solved at 2.0 Å resolution with one molecule in the asymmetric unit. The two domains are connected by a helical linker. Their interface is mostly constituted by hydrophobic interactions.