Western blot using GeneTexs affinity purified anti-S.cerevisiae Mer2 pS30 antibody shows detection of phos-phorylated Mer2 but not phosphatase treated or mutant cells. Lane 1 contains Mer2-myc protein detected in wild type cells after first immunoprecipitating the protein using anti-myc antibody. Cells were harvested 4 h after the initiation of meiosis and therefore contain mostly phosphorylated Mer2. Lane 2 contains the same preparation after treatment with phosphatase. Lane 3 contains Mer2-S30A protein as a phosphorylation control. This antibody appears to be specific for phosphorylated Mer2 at the S30 position with negligible cross reactivity against unphosphorylated protein. The primary antibody was used at a 1:5,000 dilution.