Radiolytic protein surface mapping

We report that high energy beta particles may function as a means for mapping the surface of a protein. Comparable to Fe-EDTA in the presence of ascorbate and peroxide, Y-90-EDTA alone can break polypeptide backbone bonds on the surface of E. coli RNA polymerase. The two methods give very similar fragmentation patterns, although some unique fragments are produced by each. Radiolytic footprinting may prove useful for mapping proteins inside living cells, since beta-radiolysis produces reactive species up to approximate to 1 cm away from the emitting Y-90. (C) 1996 Academic Press, Inc.