Using this criterion we constructed GlnJ variants with the following substitutions: R17K, Q42H, N54D, K85R, V100M and E109G (in each position the residue in GlnJ was replaced by the corresponding one in GlnB). These variants were expressed and purified as N-terminal selleck chemicals histidine tagged fusions. Figure 1 Alignment of the amino acid sequence of the R. rubrum GlnB and GlnJ proteins, constructed using ClustalW (http://www.ebi.ac.uk/Tools/clustalw2/index.html).
The loop regions are highlighted and the positions of the amino acid substitutions used in this study are marked with a star. Although not all the residues selected are located in regions of the PII protein that have previously been shown to be involved in metabolite binding, we decided to analyze amino acids occurring in areas of high conservation as, due to the considerable flexibility of the PII structure, they may also play a role in this response to divalent cations. An example of this high flexibility comes from the recent structure of S. elongatus Vistusertib GlnB, where the
very C-terminal portion of the protein displays a large conformational change upon binding of the ligands to the T-loop region [9]. Uridylylation of GlnJ variants in the presence of Mn2+ and Mg2+ Using purified GlnD and GlnJ variants we analysed the uridylylation profile in the conditions that were previously determined [11] and described in the Materials and methods, with click here either Mg2+ or Mn2+ present in the assays. As shown in Figure 2, GlnJ is only extensively modified in the presence of Mn2+ (A) while GlnB is modified with both Mn2+ and Mg2+ (B), as analyzed by native PAGE, with a slower migrating band
converted to a faster migrating band (all 3 subunits modified). The identity (and uridylylation status) of the two forms was also confirmed by mass spectrometry (results not shown). The GlnJ variants R17K, V100I and E109G showed the same pattern as GlnJ (Figure 2A). The GlnJN54D variant can still be modified in the presence of Mn2+ albeit to a lower extent, but there was also no modification in the presence of Mg2+. The variants GlnJQ42H and GlnJK85R show normal uridylylation in the presence of Mn2+ but enhanced with Mg2+(Figure 2A). Given the fact that only the GlnJQ42H and GlnJK85R substitutions Acetophenone supported modification with Mg2+, we combined them and constructed the GlnJQ42HK85R variant. In this case, the modification in the presence of Mn2+ was identical to GlnJ, but substantially improved with Mg2+ (Figure 2A). Figure 2 Uridylylation of GlnJ (A) and GlnB (B) variants. The reactions were performed as described in the Materials and methods in the presence of Mn2+, Mg2+ or without either divalent cation (control – C), and the uridylylation status analyzed by native PAGE. U – unmodified, M3- modified (fully modified trimmers).
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