The reaction of ribonuclease inhibitor with modified ribonucleases

Publisher Website
Google Scholar
Abstract
The effect of chemical modification of ribonuclease on its reaction with ribonuclease inhibitor has been studied. Removal of free amino groups from the enzyme with nitrous acid or by acetylation did not affect the reaction. Some changes altered the stoicheiom-etry of the reaction and ribonuclease S was found to be inhibited linearly by increasing amounts of ribonuclease inhibitor, in contrast with ribonuclease A, which is inhibited in a non-linear way. One derivative of ribonuclease containing dimethylaminonaphthalene-sulfonyl groups actually reacted with ribonuclease inhibitor to a greater extent (and linearly) than did the unaltered enzyme. The positively charged histidine at the active site and the active enzyme did not appear to be necessary for the reaction since 1-carboxymethylhistidine-119-ribonuclease reacted with ribonuclease inhibitor to almost the same extent as the native enzyme. In general, any significant change in the conformation of ribonuclease was accompanied by a loss in its ability to combine with inhibitor. The presence of 8[image]-urea also prevented reaction of ribonuclease with inhibitor. Some characteristics of the reaction of ribonuclease inhibitor, ribonuclease and deaminated ribonuclease with RNA [ribonucleic acid] and deaminated RNA were investigated.