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Dimerization of the testis brain RNA-binding protein (translin) is mediated through its C-terminus and is required
1Center for Research on Reproduction and Women's Health and Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA.
Abstract:
Testis brain-RNA-binding protein (TB-RBP) is a single-stranded DNA- and RNA-binding protein that is involved in chromosomal translocations, mRNA transport and translational regulation. Here we show from in vitro and in vivo protein binding studies that TB-RBP dimers are the minimum structural unit needed for DNA- and RNA-binding. Truncation studies demonstrate that the C-terminus of 55 amino acids of TB-RBP is essential, but not sufficient for DNA- or RNA-binding, and deletion of the leucine zipper motif in the C-terminus abolishes DNA- and RNA-binding. Changing cysteine 225 in the C-terminus to alanine does not significantly reduce DNA- or RNA-binding, but reduces the stability of the dimer. We conclude that the leucine zipper motif is required to maintain two molecules of TB-RBP as a dimer which is stabilized by a disulfide bond involving cysteine 225.