A protein isolated from Escherichia coli, identified as GroEL, reacts with anti-β spectrin antibodies

We found that a protein of molecular weight close to 65 kDa, present in Escherichia coli cells, reacts with anti-β spectrin antibodies. A method of purification of this protein was designed. The method consists of the following: nonionic detergent extraction, gel filtration chromatography, ion-exchange chromatography using DEAE–Servacell, and two FPLC ion-exchange chromatography runs: the first without urea, the second in its presence. This method allowed us to obtain a highly purified protein. The results of mass spectrometry analysis suggest that the investigated protein is GroEL (Hsp60 Class). Using computer programs, by sequence analysis of both proteins we tried to explain why GroEL isolated from E. coli reacts with anti-β spectrin antibodies. Both proteins may share a single epitope for the antibodies on their surfaces. Additionally, such an assumption is supported by the results of experiments in which antibodies interacting with GroEL were obtained from anti-β spectrin serum and were shown to react with both GroEL and β spectrins.