Study on plant RNAases. Isolation and properties of several activities from Vicia faba root cells

Vicia faba root cells contain several nucleolytic activities: phosphomonoesterase and phosphodiesterase (which however were not studied in details), one nuclease and four ribonucleases. These results were obtained by separating the extracted proteins into anionic and cationic species by chromatography on CM-cellulose at pH 5.5 and analysing each kind of proteins. Anionic species were subjected to chromatography on DEAE-cellulose which lead to isolation of one nuclease (A1) and two RNAases (A2, A3), the properties of which were studied. It was shown that the RNAases pH optima are near 6; A2 is more thermolabile than A3; both are endonucleases unable to attack double-stranded structure; studies with homopolymers, i.e. poly(A), poly(I), poly(C), poly(U), showed that their base specificities were analogous to that of already known plant RNAases. The cationic proteins, analysed with CM-cellulose, contain two RNAases (C1, C2). The pH optima were near 6 and 7, respectively; C1 is much more thermolabile than C2; both were endonucleases inactive on double-stranded structures. C1 and C2 hydrolysed poly(C) and poly(U) but not poly(A) and poly(U).