Molecular and structural characteristics of house fly brain acetylcholinesterase.

Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) from the brains of house flies (Musca domestica L., tetrachlorvinphos-resistant strain) was examined for molecular and structural features, including molecular weight, Stokes radii, partial specific volumes, sedimentation coefficients and frictional ratios. Acetylcholinesterase purified by affininity chromatography was examined in the electron microscope by negative staining and three molecular forms were clearly observed (monomers, dimers and tetramers). Several tetrameric configurations were observed as well as structures of similar size showing tails. In the preparations of acetylcholinesterase so far examined, no globular structures having more than four monomeric units were observed.