Abstract: A biotinylated probe was used for detection of endogenous ligands of a human brain lectin on blotted human brain soluble proteins. Of the various proteins from brain extract resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, five reacted with the biotinylated probe. After elimination of saccharidic moieties by periodic treatment of the same extract, a single band with Mr∼ 43,000 was recognized by the lectin. This band was identified as actin using an anti-actin antibody. These results were confirmed by binding of biotinylated lectin to purified actin.