Morphological localization of PNS myelin proteins

The localization of PNS myelin protein was studied using two methods: (1) lactoperoxidase catalysed iodination of intraperiod band material, (2) solubilization of basic proteins with ammonium acetate--Triton X-100 solutions. When myelin was swollen in the presence of lactoperoxidase and subsequently submitted to lactoperoxidase catalysed iodination P0 and what appeared to be the X protein labeled with 125I. In specimens which were disrupted in 50% ethyl alcohol, the basic proteins P1 and P2 were also iodinated. When the lactoperoxidase was omitted, there was no labeling of proteins. Ammonium acetate--Triton X-100 solutions solubilized basic proteins from both whole nerve and purified myelin preparations. Electron microscopic changes which accompanied this modification included swelling and splitting of the main period band. These data indicate that the P0 and X proteins are available for iodination in the intraperiod band of swollen PNS myelin and that basic proteins are localized in the main period band.