The effect of the 4D5 scFv-barnase-His5 on EGFP fluorescence indicates that the introduced barnase functions as a ribonuclease inside the cells.
The encoded protein functions as a ribonuclease and is required to produce the active small RNA component that represses gene expression, which may affect the biogenesis of miRNA [ 54].
Interestingly, while assessment of other TA modules did not reveal the prevalence observed for the pTRACA22 RelBE, the MazF toxin, which also functions as a ribonuclease and blocks translation by the same mechanism as RelE [ 32, 41, 48], did exhibit an increased prevalence in the human gut microbiome as well as other environments, albeit to a lesser extent (Fig 3c).
Ang may function as a tRNA-specific ribonuclease that binds to actin on the surface of endothelial cells; once bound, angiogenin is translocated to the nucleus, promoting the endothelial invasiveness necessary for blood vessel formation.
Given that the e variant contains two ribonuclease domains, we expect it to function as a monomer and the d variant with one ribonuclease domain to function as a dimer.
The role of Asp117 might be either merely to orient the correct tautomer of the His48 imidazole ring for catalysis, as in ribonuclease A,[ 34] or to reduce the pKa of the histidine NE-2 proton, thereby assisting its function as a catalytic acid.
In turn, Cas13 enzymes function as RNA-guided ribonucleases whose non-specific activity is triggered by target RNA binding.
Furthermore, the R. belli and TRG rickettsiae genomes have elevated levels of predicted PIN-domain proteins (homologs of the pilT N-terminal domain), which in eukaryotes function as ribonucleases [163], [164] involved in RNAi and nonsense-mediated RNA degradation [162], [163].
