Irreversible contraction of inclusion bodies was found to have a huge impact on sedimentation velocity,solubility and extractability of target protein firom non-classical inclusion bodies.This also affects the downstream process during protein isolation from non-classical IBs.The similarities with protein deposits in conformational diseases are discussed as well Based on extractability studies accompanied by electron mieroseopy,a hypothetical model of IBs formation mechanism is presented,which is supported by usually observed single IB per E.coli cell.