BIOCHEMICAL-EVIDENCE FOR THE PRESENCE OF AN UNCONVENTIONAL ACTIN PROTEIN IN A PROKARYOTIC ORGANISM

The ubiquity of actin, like the functional diversity of many associate d proteins, raises a question concerning diversification of motility m echanisms and thus the emergence of an elementary functional system. O ur aim was to investigate, in particular, mobiles prokaryotics cells a s Synechocystis lacking cilia and flagella, search for actin essential properties and then locate the molecular behaviours. Here we report t he presence and purification of a 56-kDa (apparent molecular weight) p rokaryotic protein that polymerizes to form filaments, activates myosi n Mg++-ATPase activity, inhibits DNase-1 activity and affords close an tigenic homology to skeletal actin. This protein was found to be assoc iated with thylakoid membranes and extracted in the presence of Triton X-100.