Rabbit Anti-Human LIG4 (a.a. 51-150) Polyclonal antibody

The coordination chemistry of chiral tetradentate dianionic ligands of the diamine-diphenolato and diamine-diolato families having the (R,R)-2,2-bipyrrolidine core around ZnII was investigated. Reactions with diethylzinc led to complexes of the type [{ONNO}Zn] for most ligands and to bridging dinuclear complexes of the type [-Lig4(ZnEt)2] for one of the diamine-diolato ligands. Reactions with bis(hexamethyldisilazide)zinc led to complete conversions. Most complexes were obtained as mononuclear complexes. The least bulky Salan ligand, Lig3, led to an equilibrium between mononuclear and dinuclear complexes in noncoordinating solvents. All ligands were found to wrap around the tetrahedral zinc with very high diastereoselectivities supporting predetermined chiral induction from the bipyrrolidine core to the helical ligand wrapping. Molecular structures determined by single-crystal X-ray diffraction for two complexes of the type [{ONNO}Zn] substantiated the predicted wrapping of the (R,R)-based ligands. In contrast, representative Salan and diamine-diolato ligands assembled around the trans-1,2-diaminocyclohexane core led to diastereomer mixtures of the corresponding complexes.

Background: The yeast CDCS gene encodes a DNA ligase I activity required during nuclear DNA replication to ligate the Okazaki fragments formed when the lagging DNA strand is synthesised. The only other DNA ligase predicted from the yeast genome sequence, DNL4/LIG4, is specifically involved in a non-homologous DNA end-joining reaction. What then is the source of the DNA ligase activity required for replication of the yeast mitochondrial genome? Results: We report that CDCS encodes two distinct polypeptides expressed from consecutive in-frame AUG codons. Translational initiation at these two sites gives rise to polypeptides differing by a 23 residue amino-terminal extension, which corresponds to a functional mitochondrial pre-sequence sufficient to direct import into yeast mitochondria. Initiation at the first AUG codon results in a 755 amino-acid polypeptide that is imported into mitochondria, whereupon the pre-sequence is proteolytically removed to yield the mature mitochondrial form of Cdc9p. Initiation at the second AUG codon produces a 732 amino-acid polypeptide, which is localised to the nucleus. Cells expressing only the nuclear isoform were found to be specifically defective in the maintenance of the mitochondrial genome. Conclusions: CDCS encodes two distinct forms of DNA ligase I. The first is targeted to the mitochondrion and is required for propagation and maintenance of mitochondrial DNA, the second localises to the nucleus and is sufficient for the essential cell-division function associated with this gene.