The plasma membrane of Avena coleoptile protoplasts.

Treatment of living protoplasts from the Avena coleoptile with enzymes and chemicals has provided new information about the external surface of the plasma membrane. Treatments with selected detergents and polyene antibiotics indicate that little sterol is present. The lysis of protoplasts in carboxymethyl-RNase which is enzymatically almost inactive provides strong evidence that the lysis previously observed in RNase is not an indication of RNA in the membrane. Divalent cations inhibit the RNase-induced lysis, indicating that such lysis involves the interaction of RNase with negatively charged sites on the plasma membrane surface. Tyrosinase treatment gives no lysis, showing that tyrosine does not play the role in these plasma membranes attributed to it in some animal cells. Peroxidase does not harm coleoptile protoplasts.