Phy M: an RNase activity specific for U and A residues useful in RNA sequence analysis.

Physarum polycephalum, an acellular slime mold, produces an endoribonuclease activity (Phy M) useful in direct RNA sequence determination. Under conditions previously described for direct enzymatic RNA sequencing (7M urea, 50 degrees C, pH 5.0)1 Phy M cleaves almost exclusively and uniformly at Up-N and Ap-N. In the absence of urea Up-N, Ap-N, and Gp-N are attacked in a sequence specific way identical to that found with RNase Phy I2 digests performed under the same reaction conditions.