Association of an axonally transported polypeptide (H) with 100-A filaments. Use of immunoaffinity electron microscope grids.
Polypeptide H (mol wt 195,000) is axonally transported in rabbit retinal ganglion cells at a velocity of 0.7--1.1 mm/d, i.e., in the most slowly moving of the five transport groups described in these neurons. To identify the organelle with which H is associated, we purified H, prepared antibodies directed against it, and adsorbed the antibodies onto Formvar-coated electron microscope grids. When the resulting "immuno-affinity grids" were incubated with extracts of spinal cord and then examined in the electron microscope, they contained as many as 100 times more 100-A filaments than did grids coated similarly with nonimmune IgG. The ability of the anti-H IgG to specifically adsorb filaments to grids was completely blocked by incubating the IgG with polypeptide H. The 100-A filaments adsorbed to anti-H immunoaffinity grids could be specifically decorated by incubating them with anti-H IgG. These observations demonstrate that H antigens (and most likely H itself) are associated with 100-A neurofilaments. In addition, they suggest that the use of immunoaffinity grids may be a useful approach for determining the organelle associations of polypeptides.
D000818:Animals; D001370:Axonal Transport; D003599:Cytoskeleton / Q000378:metabolism*; D007163:Immunosorbent Techniques; D008854:Microscopy, Electron / Q000379:methods; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism*; D011817:Rabbits; D013116:Spinal Cord / Q000378:metabolism*
D009419:Nerve Tissue Proteins