Crystallization and preliminary X-ray diffraction studies of the metal-ion-mediated ternary complex of the HutP protein with l-histidine and its cognate RNA

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HutP is an RNA-binding protein that regulates the expression of the Bacillus subtilis hut operon by binding to cis-acting regulatory sequences within hut mRNA, exclusively in the presence of l-histidine. We recently solved the crystal structure of a binary complex (HutP with an l-histidine analog) that revealed a novel RNA-binding fold, and identified the important residues that interact with the l-histidine analog. In addition, we have defined the minimal RNA binding segment that is required for HutP recognition. Interestingly, we showed that ternary complex formation depends on the availability of not only l-histidine but also divalent metal ions. Here we report the crystallization and preliminary X-ray diffraction analysis of the HutP ternary complex. The ternary complex was crystallized in the presence of Mg 2+ along with l-histidine and hut mRNA, using the hanging drop vapor diffusion method. The crystal belongs to the R3 space group, with unit cell parameters a= b=75.30 Å, c=133.8 Å. A complete data set at 1.60 Å was collected.