In addition, these antisera immunoprecipitate RNase P activity from this partially-purified RNase P. In this experiment, immune serum or preimmune serum was bound to protein A sepharose beads, and then the partially-purified RNase P was passed through the beads. The beads were washed to remove residual activity, and then anything bound was eluted by washing twice with buffer at 72C, and RNase P activity was assayed in the various fractions. As you can see, protein A beads bound with the immune serum, but not preimmune sserum (or no serum), depleted RNase P activity from the flow-through, and this activity was released from the column during the elution step. The ability of antibodies from rabbits immunized against these proteins to retain RNase P activity shows that these proteins and RNase P activity are physically associated, i.e. these proteins are RNase P subunits.