form furthermore strong denaturants have heretofore been necessary for their subsequent solubilization this invention allows for the solubilization of insoluble proteins after bacterial expression the methods of this invention in contrast with other methods of solubilizing proteins do not require denaturation and subsequent renaturation of the protein this is a particular advantage for the classes of protein which cannot be renatured the methods of this invention therefore allow for commercial use of bacterial expression for many proteins heretofore not suitable for bacterial expression because it yields soluble nondenatured protein this invention comprises two procedures for lysing the bacteria and fractionating the lysates consisting of 1 lysing the bacteria by a light lysozyme digestion followed by the addition of sarkosyl detergent and several obligate steps of fractionation following lysis and 2 lysing the bacteria by other standard methods collecting the insoluble protein and extracting this insoluble protein with sarkosyl detergent and edta followed by fractionation a protein which may be solubilized after bacterial expression by the methods of this invention is actin in either its full length 42 kda form or in a truncated 29 kda mutant form actin is normally a soluble protein its insolubility after bacterial expression and lysis may be due to co aggregation of the actin with bacterial outer membranes during bacterial lysis this method can also be used on other proteins including dictyostelium discoideum myosin light chain kinase sarkosyl detergent is a relatively mild chaotrope with a specific effect upon this co aggregation process since it does not solubilize the bacterial outer membrane the.