uncharacterized subfamily of the LabA-like PIN domain of Synechococcus elongatus LabA (low-amplitude and bright) and related proteins
The LabA-like PIN domain family includes Synechococcus elongatus PCC 7942 LabA which participates in cyanobacterial circadian timing, it is required for negative feedback regulation of the autokinase/autophosphatase KaiC, a central component of the circadian clock system, and appears to be necessary for KaiC-dependent repression of gene expression. It also includes the N-terminal domain of limkain b1, a human autoantigen localized to a subset of ABCD3 and PXF marked peroxisomes, human ZNF451, uncharacterized Bacillus subtilis YqxD, uncharacterized Escherichia coli YaiI, and the N-terminal domain of a well-conserved group of mainly bacterial proteins with no defined function, which contain a C-terminal LabA_like_C domain. Curiously Pseudomonas putida S16 NicB, which is described as a putative NADH-dependent hydroxylase involved in the microbial degradation of nicotine also falls into this family. The PIN (PilT N terminus) domain belongs to a large nuclease superfamily. 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.
Comment:based on structure and experimental evidence from PIN-superfamily members belonging to the FEN-like, VapC-like, PRORP-like, and LabA-like families
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. Some members of the superfamily lack several of these key catalytic residues. In this subgroup 4 conserved catalytic residues are found.
Jiyao W et al.(2023). "The conserved domain database in 2023.",