N-terminal LabA-like PIN domain of limkain b1 and similar proteins
Limkain b1 is a human autoantigen, localized to a subset of ABCD3 and PXF marked peroxisomes. Limkain b1 may be a relatively common target of human autoantibodies reactive to cytoplasmic vesicle-like structures. Limkain b1 contains multiple copies of LOTUS domains and a conserved RNA recognition motif, this and similar domain architectures are shared by several members of this family, and a function of these architectures in RNA binding or RNA metabolism has been suggested. The function of the N-terminal domain is unknown. This subfamily belongs to LabA-like PIN domain family which includes Synechococcus elongatus PCC 7942 LabA, human ZNF451, uncharacterized Bacillus subtilis YqxD and 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, a gene labeled NicB from Pseudomonas putida S16, which is described as a putative NADH-dependent hydroxylase involved in the microbial degradation of nicotine also falls into the LabA-like PIN 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, 3 conserved catalytic residues are found.
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