Evidence that the bovine spinal cord protein is not an intrinsic component of peripheral myelin.
Bovine spinal cord protein from peripheral nerve (BSCP-PN) was detected in the soluble fraction of the initial 0.8 M sucrose homogenate of bovine peripheral nerves by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The BSCP-PN in the soluble fraction of the 0.8 M sucrose homogenates was 25% of the BSCP-PN found in the soluble fraction of 0.3 M NaCl homogenates of peripheral nerve. BSCP-PN was also identified in purified bovine peripheral nerve myelin by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Densitometry data indicated that the BSCP-PN in myelin decreased from 25% of the total protein to approximately 8% when myelin was extracted with 0.3 M NaCl or 0.05 M HCl. The protein that remained in the BSCP-PN band of the NaCl-extracted myelin was identified as the periodic acid-Schiff II glycoprotein of peripheral myelin. Basic proteins such as BSCP-PN or lysozyme bound to myelin and to NaCl-extracted myelin when they were added to homogenates of myelin in 0.8 M sucrose. Pepsin, an acidic protein, did not bind to myelin under the same conditions. The results suggest that in 0.8 M sucrose, positively charged BSCP-PN released from the cytoplasm by homogenization binds to negatively charged myelin; thereafter, the BSCP-PN-myelin complex remains intact until it is dissociated in media of sufficiently high ionic strength. This interpretation is consistent with the immunohistological studies which demonstrated that BSCP-PN was not in the myelin sheath but was clearly localized in axons and in, or adjacent to, the Schwann cell basement membrane.
D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D009113:Muramidase; D009185:Myelin Proteins / Q000032:analysis*; D009186:Myelin Sheath / Q000032:analysis*; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009994:Osmolar Concentration; D010434:Pepsin A; D010525:Peripheral Nerves / Q000032:analysis*; D011485:Protein Binding; D013116:Spinal Cord / Q000032:analysis*
D009185:Myelin Proteins; D009419:Nerve Tissue Proteins; D009113:Muramidase; D010434:Pepsin A