Cloning and expression of cDNA coding for bouganin

Abstract

Bouganin is a ribosome‐inactivating protein that recently was isolated from Bougainvillea spectabilis Willd. In this work, the cloning and expression of the cDNA encoding for bouganin is described. From the cDNA, the amino‐acid sequence was deduced, which correlated with the primary sequence data obtained by amino‐acid sequencing on the native protein. Bouganin is synthesized as a pro‐peptide consisting of 305 amino acids, the first 26 of which act as a leader signal while the 29 C‐terminal amino acids are cleaved during processing of the molecule. The mature protein consists of 250 amino acids. Using the cDNA sequence encoding the mature protein of 250 amino acids, a recombinant protein was expressed, purified and characterized. The recombinant molecule had similar activity in a cell‐free protein synthesis assay and had comparable toxicity on living cells as compared to the isolated native bouganin.