Crosslinked products with pb2(220)-DHFR (A) or pb2Δ19(220)-DHFR (B) containing 2 at the indicated positions were analyzed by immunoprecipitation with antibodies against Tom40, Tim44, and Ssc1p. The major crosslinked products immunoprecipitated with one of these antibodies are indicated with arrowheads. αTom40, antibodies against Tom40; αTim44, antibodies against Tim44; αSsc1p, antibodies against Ssc1p.