Type 1 ribosome-inactivating proteins are the most abundant proteins in iris (Iris hollandica var. Professor Blaauw) bulbs: characterization and molecular cloning.

The most abundant protein of Iris bulbs has been identified as a type 1 ribosome-inactivating protein (RIP). Analysis of the purified proteins and molecular cloning of the corresponding cDNAs demonstrated that this type 1 RIP is a mixture of three isoforms that exhibit a high degree of sequence identity and have similar, though not identical, ribosome-inactivating and polynucleotide:adenosine glycosidase activities. The accumulation of large quantities of type 1 RIP in a vegetative storage organ suggests that this presumed defence-related protein also plays a role in the nitrogen-storage metabolism of the bulb.