Three proteinase inhibitor genes have been identified in the rapeseed (Brassica napus) genome. They are highly homologous to other genes of the mustard inhibitor (MSI) family of proteinase inhibitors characteristic of Cruciferae. In germinating seeds, only the transcript of one gene, coding for a trypsin inhibitor, is detectable by Northern analysis. The other two genes are transcribed at basal levels detectable only by reverse transcription PCR. One of the other two genes (rti-2) encodes a polypeptide with a glutamic residue in the P1 position, characteristic of glutamyl proteinase inhibitors. The recombinant RTI-2 protein strongly inhibits (Ki=44 nM) a glutamyl proteinase from Streptomyces griseus.