Mutations in the third repeat bind DNA when the salt bridge is intact. A. Electrophoretic mobility shift assays (EMSA) using nuclear lysates containing c-Myb VP16 (c-MybVP) wild-type and mutant fusion proteins were performed. c-MybVP lysates are labeled: – = no lysate; v/o = lysate with vector only (no c-MybVP protein); wt = wild-type; mR3-1,-2, and -3 = third repeat mutants. B. Western blot analysis of nuclear lysates used in the EMSA. The 5E Myb-specific monoclonal antibody reveals that similar wild-type and mutant proteins are present in the assay. c-MybVP lysates are labeled as in A. Bars represent the 7B SDS PAGE molecular weight markers (Sigma-Aldrich) with bands from top to bottom of 180, 116, 84, 58, 48.5, 36.5 kDa.