Oligomeric forms, functions and cellular localization of alpha-crystallin type protein from Acholeplasma laidlawii

Alpha-Crystallin type heat shock protein (alpha-HSP) IbpA from Acholeplasma laidlawii was expressed in Escherichia coil and isolated from cell extract on Ni-sepharose column. Recombinant IbpA, like other alpha-HSPs, spontaneously formed oligomeres in vitro. High resolution electron microscopy revealed regular structures with 15 nm in diameter. Evaluation of molecular mass of IbpA oligomers was performed by gel filtration. Most of oligomers consist of 24 subunits. Recombinant IbpA prevents heat denaturation of soluble proteins in cell extract of E. coli and displays a mild positive effect on thermotolerance of E. coli cells during severe heat shock. We investigated a localization of IbpA in A. laidlawii cell by immunocytochemistry. We suppose that IbpA may protect various intracellular structures from damage during heat shock.