LTW4 protein on mouse chromosome 1 is a member of a family of antioxidant proteins

Based on its map position, polymorphism pattern, and expression in the kidney, the gene encoding liver 20,000-30,000 MW protein 4 (LTW4) can be considered a potential candidate for the Jckm2 modifying. locus, which mediates the severity of polycystic kidney disease in the juvenile cystic kidney mouse, Using two-dimensional gel electrophoresis, we identified variants of a 26-kDa polypeptide that differed in their isoelectric points between the C57BL/6J anti the DBA/2J inbred strains in a pattern similar to that originally described for LTW4 protein, N-terminal amino acid sequence was obtained by microsequencing analysis, and full-length clones were obtained by RT-PCR amplification and characterized. The map position of the cloned gene was determined and corresponded to that previously described for Ltw4. The gene has homology to a class of proteins characterized as thiol-specific antioxidants that are protective against damage caused by oxidative stress. The murine MER5 gene is also a member of this gene family and has recently been renamed Antioxidant protein 1 (Aop1), based on its functional characterization, We therefore propose that the gene encoding LTW4 be called Aop2. (C) 1997 Academic Press.