PIN (PilT N terminus) domain: Superfamily; The PIN (PilT N terminus) domain belongs to a large nuclease superfamily, and were originally named for their sequence similarity to the N-terminal domain of an annotated pili biogenesis protein, PilT, a domain fusion between a PIN-domain and a PilT ATPase domain. The structural properties of the PIN 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 while some others 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. The PIN domain superfamily includes: the FEN-like PIN domain family such as the PIN domains of Flap endonuclease-1 (FEN1), exonuclease-1 (EXO1), Mkt1, Gap Endonuclease 1 (GEN1), and Xeroderma pigmentosum complementation group G (XPG) nuclease, 5'-3' exonucleases of DNA polymerase I and bacteriophage T4- and T5-5' nucleases; the VapC-like PIN domain family which includes toxins of prokaryotic toxin/antitoxin operons FitAB and VapBC, as well as eukaryotic ribonucleases such as Smg6, ribosome assembly factor NOB1, exosome subunit Rrp44 endoribonuclease and rRNA-processing protein Fcf1; the LabA-like PIN domain family which includes the PIN domains of Synechococcus elongatus LabA (low-amplitude and bright); the PRORP-Zc3h12a-like PIN domain family which includes the PIN domains of RNase P (PRORP), ribonuclease Zc3h12a; and Bacillus subtilis YacP/Rae1-like PIN domains. It also includes the Mut7-C PIN domain family, which is not represented here as it is a shortened version of the PIN fold and lacks a core strand and helix (H3 and S3). The Mut7-C PIN domain family includes the C-terminus of Caenorhabditis elegans exonuclease Mut-7.

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gi 1817927405 238 LHPErhlPGSDFVEEWMDRQVEEWRVSEkIAKLEAAS---RARALNEISEERRR 288
Cdd:cd09874    12 YVRE---PGSDAVRALLDAASDVLAISD-LTRVEFASalaRKVREGELSEEQAR 61

VapC-like PIN domain of the hypothetical protein MT3492 of Mycobacterium tuberculosis CDC1551 and other uncharacterized, annotated PilT protein domain proteins; Virulence associated protein C (VapC)-like PIN (PilT N terminus) domain of Mycobacterium tuberculosis CDC1551, hypothetical protein MT3492, and similar bacterial and archaeal proteins are included in this subfamily. They are PIN domain homologs of the Mycobacterium tuberculosis VapC and Neisseria gonorrhoeae FitB toxins of the prokaryotic toxin/antitoxin operons, VapBC and FitAB, respectively, which are believed to be involved in growth inhibition by regulating translation. These toxins are nearly always co-expressed with an antitoxin, a cognate protein inhibitor, forming an inert protein complex. Disassociation of the protein complex activates the ribonuclease activity of the toxin by an, as yet undefined mechanism. The PIN domain belongs to a large nuclease superfamily. 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.

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                  ....*....|....*....|....*....|....*....|....*....|....
gi 1817927405 238 LHPErhlPGSDFVEEWMDRQVEEWRVSEkIAKLEAAS---RARALNEISEERRR 288
Cdd:cd09874    12 YVRE---PGSDAVRALLDAASDVLAISD-LTRVEFASalaRKVREGELSEEQAR 61

VapC-like PIN domain of the hypothetical protein MT3492 of Mycobacterium tuberculosis CDC1551 and other uncharacterized, annotated PilT protein domain proteins; Virulence associated protein C (VapC)-like PIN (PilT N terminus) domain of Mycobacterium tuberculosis CDC1551, hypothetical protein MT3492, and similar bacterial and archaeal proteins are included in this subfamily. They are PIN domain homologs of the Mycobacterium tuberculosis VapC and Neisseria gonorrhoeae FitB toxins of the prokaryotic toxin/antitoxin operons, VapBC and FitAB, respectively, which are believed to be involved in growth inhibition by regulating translation. These toxins are nearly always co-expressed with an antitoxin, a cognate protein inhibitor, forming an inert protein complex. Disassociation of the protein complex activates the ribonuclease activity of the toxin by an, as yet undefined mechanism. The PIN domain belongs to a large nuclease superfamily. 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.

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                  ....*....|....*....|....*....|....*....|....*....|....
gi 1817927405 238 LHPErhlPGSDFVEEWMDRQVEEWRVSEkIAKLEAAS---RARALNEISEERRR 288
Cdd:cd09874    12 YVRE---PGSDAVRALLDAASDVLAISD-LTRVEFASalaRKVREGELSEEQAR 61