| Abstract: | A non-ionic detergent-insoluble fraction was obtained from pure cultures of chicken sympathetic neurons and further purified at the 10%-30% interface of a discontinuous density gradient. This fraction contains actin as its major component and approximately 20 further polypeptides some of which are glycosylated. Two conspicuous glycoproteins in this fraction, of molecular masses 130 kDa and 90 kDa, have been shown to bind to concanavalin A; in cultured neurons the 130-kDa glycoprotein may also be labelled with [3H]glucosamine and [3H]fucose. Both are restricted to one interface of the stepped sucrose gradient when cells are lysed in low ionic strength buffer and eluted with actin in the void volume of a Sepharose 6B column. Glycoproteins of the same molecular weight have been obtained by the same isolation procedure from 10-day-old chicken embryo brains. One-dimensional peptide maps show that the carbohydrate-containing peptides from brain and sympathetic neurons are closely similar if not identical. The glycoproteins are also present in sciatic nerve but cannot be detected in a detergent-insoluble form in rounded neurons - lacking axons - or fibroblasts. They might, therefore, be involved in the linkage of the axonal cytoskeleton to the plasma membrane. |
