In these kinds of cascade reactions, ubiquitin E3 ligases catalyze the final step of the process and govern the specificity of the modification reaction.
Both in vivo and in vitro studies indicate low substrate specificity of the modification machinery, which has been explored for re-engineering of the structures of a number of members.
It seems likely that more ligases or cofactors exist and contribute to the specificity of the modification process.
The guide region, which ensures the specificity of the modification by base pairing to the target RNA, is a region of 10 20 nucleotides found immediately upstream of the boxes D and/or D′ [5,7].
Structural studies on Ogt provided insight into how this enzyme modifies this baffling diversity of substrates: Ogt primarily binds to the peptide backbone of substrates and shows no clear specificity for the modification of specific serines or threonines (Janetzko and Walker 2014).
The absence of S-nitrosated Trim32 under GSNO treatment revealed the specificity of the above modifications (Fig 5A).
To determine the specificity of the NEMO modification, we co-transfected NEMO with either TRAF6, or various TRAF6-associated factors (TRAF2, TRAF5, constitutively-active IKKβ (IKKβEE), TAK1/TAB1, MEKK3, ASK1) known to act downstream of, or parallel to, TRAF6-dependent signaling pathways [24], [25], [26], [27], [28].
We next constructed tRNAIle2 mutants bearing the two positive elements for acC formation, to determine the minimum necessary elements for the conversion of the specificity of the wobble modification from lysidine to acC.
mad2-S189D (justwowo residues away) had no such defect, highlighting the specificity of the S187 modification and apparently ruling out any simple explanation resulting from addition of negative charge within the C-terminal Mad2p safety belt.
These differences reflect the strain-specificity of the trait modifications induced by the β-adrenergic drugs, in particular iso10.
