Protein Purification of Pir A - linker - Pir B

Abstract

Photorhabdus insect-related toxins A and B (Pir A and Pir B) are two different types of insecticidal toxins that were firstly found in Photorhabdus luminescens. Its homolog, from Vibrio parahaemolyticus, is found to cause acute hepatopancreatic necrosis disease (AHPND) in the shrimp, since it contains plasmid pVA1. When binded together, Pir A and B can exert its effect, because they form a structure similar to Cry protein, a pore-forming protein that can kill insects. However, the binding affinity between Pir A and B is small enough, leading to hardness to form the crystal structure, hence a sequence of linkers is added to stabilize the protein. Thus, the aim of this research is to purify the Pir A-linker-Pir B protein with some chromatographic methods, namely affinity and gel filtration chromatography, and study the 3D structure using crystallization and x-ray diffraction method. It is found that the chromatogram of the results contains only one high peak, with the actual concentration of 32.2 mg/mL. Although the research achieved the purification protein, the study of 3D structure of the protein could not be processed due to time limitation.