AXONAL PROTEINS INVOLVED IN MYELINATION - CHARACTERIZATION OF A COLLAGEN-LIKE PROTEIN

An anti-axolemma monoclonal antibody, designated G21.3, has been isola ted in order to understand molecular mechanisms involved in myelinatio n. Both biochemical and morphological studies showed that the monoclon al antibody inhibits myelin production by oligodendrocytes in cerebell ar slice cultures. On Western blots of axolemma preparations, the anti body recognized 140- and 120-kD proteins. The present study involves t he isolation and characterization of the G21.3 antigen. The G21.3-immu noreactive proteins of 140 and 120 kD were purified from the adult rat sciatic nerve and amino acid sequencing of these proteins revealed si gnificant homology to alpha I and alpha II chains of collagen type I. Biochemical and Western blot analysis using pure collagen, collagen I antibody and collagenase D suggest that the antigen isolated from scia tic nerve is collagen. However, immunofluorescence studies using the G 21.3 antibody, collagen I antibody, collagenase D and Northern blot an alysis using a collagen probe do not fully support the view that the G 21.3 antigen in the CNS is also a collagen. We conclude that the G21.3 antigen is a collagenlike protein involved in CNS myelination.