VapC-like PIN domain of Haemophilus influenzae VapC1 and related proteins
Haemophilus influenzae VapC1 has endonucleolytic activity with RNA, it cleaves initiator tRNA between the anticodon stem and loop, but does not cleave mRNA, rRNA or tmRNA, and has no activity on ssDNA or dsDNA. This subfamily belongs to the PIN_VapC4-5_FitB-like subfamily of the VapC (virulence-associated protein C)-like family of the PIN domain nuclease superfamily. VapC is the PIN-domain ribonuclease toxin from prokaryotic VapBC TA systems. VapB is a transcription factor-like protein antitoxin acting as an inhibitor. FitB is a toxin of the FitAB TA system. Other members of the VapC-like nuclease family include eukaryotic ribonucleases such as Smg6, ribosome assembly factor NOB1, exosome subunit Rrp44 endoribonuclease and rRNA-processing protein Fcf1. The structural properties of the PIN (PilT N terminus) domain indicate its active center, consisting of three highly conserved catalytic residues which coordinate metal ions, in some members, additional metal coordinating residues can be found. Some members of the superfamily lack several of these key catalytic residues. The PIN active site is geometrically similar in the active center of structure-specific 5' nucleases, PIN-domain ribonucleases of eukaryotic rRNA editing proteins, and bacterial toxins of toxin-antitoxin (TA) operons.
Comment:based on homology with related nucleases with structure including VapC toxin from Shigella flexneri 2a virulence plasmid pMYSH6000 and on experimental evidence
Comment:The PIN domain superfamily contains three highly conserved catalytic residues which coordinate metal ions; in some members, additional metal coordinating residues can be found while some others lack several of these key catalytic residues.
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