Recently we described the production of two monoclonal antibodies 10G2 and 10C4 of IgG3 subclass raised against the recombinant tms1 protein of fission yeast. Here we introduce a new monoclonal antibody 2E2 of IgG1 subclass and present the precise epitope mapping of these monoclonal antibodies using tms1 deletion mutants and synthetically produced oligopeptides spanning the tms1 protein by immunoblot analysis.