Cysteine proteinase inhibitors: purification and gene isolation

Abstract

Genetic engineering has produced a transgenic insect- resistant plant which produces a serine protease inhibitor (Hilder et al., 1987). More insects can be targetted if a plant can be made to produce thiol protease inhibitors. Hence this project attempts to do some preliminary work - purification and gene isolation of thiol protease inhibitors, which is necessary before plants resistant to insects using thiol proteinases as their digestive enzymes can be created. It is known that cowpea seeds contain thiol protease inhibitors. However, their protein sequences have never been elucidated. In the first part of the project, _it was attempted to obtain a pure thiol protease inhibitor. This was so that its sequence could be determined partially to construct an oligo-nucleotide probe to pick the gene coding for it from a cDNA library. In the second part of the project, it was attempted to isolate the gene coding for the bromelain inhibitor of pineapple, to clone it up and to sequence it. Though the sequence of this inhibitor has been known for years, its gene has never been isolated or sequenced.