Characterization of the Mouse Autoantigen La (SS-B): Identification of Conserved RNA-Binding Motifs, a Putative ATP Binding Site and Reactivity of Recombinant Protein with Poly(U) and Human Autoantibodies

Abstract

To facilitate the study of autoimmunity to the nuclear Ag La (SS-B) we have isolated characterized cDNA encoding the mouse La (SS-B) protein. Mouse La (SS-B) protein has 76.7% identity to both human and bovine La (SS-B) proteins and the previously recognized RNP-binding motifs were noted to be highly conserved across the three species. Examination of the primary sequence of human and bovine La (SS-B) newly identifies the site of a potential ATP-binding motif G/AXXXXGK which is preserved in mouse La (SS-B) despite a unique 16 amino acid insertion present in this region of the mouse protein. Analysis of mouse genomic DNA suggests a single gene encodes mouse La (SS-B) and no restriction fragmen..