A homologous connection (with N104) is found in NmFic [8]. Most relevant for catalysis is the orientation of the -phosphate that has to be accessible for nucleophilic assault by the prospective side-chain hydroxyl group. death. Mutational and bioinformatics analysis indicated that Fic proteins containing a purely conserved HxFx(D/E)GNGRxxR signature motif in the active center typically display adenylylation activity [1], [2], [3], [4], [5], while Fic proteins with an active center deviating from this consensus are considered to have used different activities. Indeed, the host-targeted LY310762 effector protein AnkX of exhibiting an HxFxDANGRxxV signature motif displays phosphocholination activity for the GTPase Rab1 [6]. The FIC website is structurally characterized by a conserved central core of four helices (2 to 5) that is flanked by three helices (1, 6 and 7) found in diverse dispositions in different Fic proteins [3], [7]. Helices 4 and 5 are joined by a loop that together with the N-terminal cap of helix 5 forms the active center represented by a signature motif with the consensus sequence HxFx(D/E)GNGRxxR. The catalytic mechanism of adenylylation was deduced from your crystal structure of the second FIC website of IbpA in complex with the adenylylated Cdc42 target [4] and from biochemical studies [5] and shown to involve nucleophilic assault of the prospective side-chain hydroxyl onto the ATP -phosphate. The triphosphate binding site in the anionic nest in the N-terminus of helix 5 was characterized by the crystal structure of BepA from in complex with pyrophosphate, the side product of the reaction [3]. An ATP substrate complex structure was acquired recently for the Fic protein of causes bacterial growth arrest when overexpressed in or and that this effect can be repressed by co-expression with the anti-toxin VbhA, a small protein encoded upstream of VbhT [8]. As demonstrated by structure analysis, VbhA forms a tight complex with the FIC website of VbhT with the conserved glutamate (Einh) from your inhibitory helix inh partly obstructing the ATP binding site, which offered a first idea concerning the inhibitory mechanism mediated by VbhA binding. Exhaustive bioinformatic analysis coupled with homology modeling exposed the (S/T)xxxE(G/N) signature motif of inh isn’t just found in several other putative anti-toxin sequences coded immediately upstream of Fic proteins, but is often part of the FIC website itself either preceding helix 1 or immediately following helix 7 [8]. Therefore, a classification system was launched grouping the Fic proteins for which an anti-toxin with an inhibitory helix inh had been found into class I and those with an equivalent of inh in the N- or C-terminal part of the Fic protein into classes II and III, respectively. Indeed, 90% of the Fic proteins with the canonical FIC signature motif could be classified accordingly, suggesting that all these enzymes are inhibited in their enzymatic activity. The physiological stimulus or condition for alleviation of inh-mediated inhibition is not yet known. For T4SS Fic proteins LY310762 of class I (such as VbhT or BepA [9]), however, it appears likely that, for injection into sponsor cells, the Fic protein has to unfold and will be translocated without the antitoxin. For class II and III proteins, detachment, unfolding, or proteolytic cleavage of the inh helix may cause alleviation of inhibition. In fact, a truncation mutant of the class III Fic protein from (NmFic) lacking the entire C-terminal inh helix showed strong ATase activity and allowed to study the catalytic and inhibitory mechanism in detail [8]. A more subtle means to reduce inhibition, which is applicable to Fic proteins of all three classes, is the alternative of the inhibitory glutamate by glycine. AMP transfer to the small GTPases Rac1 and Cdc42, whereas only marginal effect was seen with the wild-type proteins [8]. Here, we assayed inside a systematic approach Fic associates of the three Fic classes and LY310762 their E->G mutants for adenylylation showing the mutation causes inhibition alleviation across the Fic classes. Binding of ATP substrate or AMPPNP substrate analog to the wild-type and the E->G mutant proteins was analyzed by protein crystallography to Rabbit Polyclonal to SYT13 reveal the inhibitory mechanism and to get further insight into catalysis. This yielded a consistent molecular mechanism that most likely applies to most adenylylation proficient Fic proteins irrespective of class. Materials and Methods Cloning The full-length gene and part of the gene (amino acid residues 1C248, His6-tagged) were amplified from plasmid pPE0021 and cloned into the pRSF-Duet1 vector leading to plasmid pAG0077 (VbhA/VbhT(FIC)). The full-length gene and part of the gene encoding the FIC website (amino acid residues 1C198, His6-tagged) were PCR-amplified from plasmid pPE0021 and cloned into the pRSF-Duet1 vector (pFVS0011). A two-base pair mutation is then launched in pFVS0011 to obtain plasmid pFVS0065 (VbhAE24G/VbhT(FIC)). The gene of was PCR-amplified with an N-terminal His6-tag from from coding region of amino acid residues 11C191 to generate plasmid expressing NmFic (pFVS0015). The E186G mutant create (NmFicE186G, pFVS0059) was generated by introducing a.
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