Purification and characterization of a protein that binds to the recombination signal sequence of the immunoglobulin Jx segment

摘要

A protein that binds to the recombination signal sequence (RS) of the immunoglobulin J_x segment was purified almost to homogeneity from the nuclear extract of a murine pre-B cell line 38B9. A similar binding protein was found in lymphoid cell lines but not in non-lyrnphoid cell lines. The binding activity was associated with a polypeptide with a molecular weight of 60,000. DNase I footprinting analysis demonstrated that this binding protein interacted with the heptamer and several 3′ bases close to the heptamer. The Kd value of the J_x RS binding protein to the J_x RS was 1 nM. One base substitution in the heptamer of the J_x RS greatly reduced the affinity of the J_x RS binding protein. The high specificity of the binding site of the J_x RS binding protein suggests that this protein may be involved in V-J recombination.