We have isolated a cDNA clone encoding an integrin (Itg) beta-subunit polypeptide from a rat cerebral cortex oligodendroglia cDNA library. This beta-subunit was previously designated beta OL (OL for oligodendroglia), since it had an M(r) that differed from that of the rat fibroblast beta 1 protein. The complete nucleotide sequence encoding the signal sequence and mature protein was determined. Comparison of the deduced amino acid (aa) sequence of beta OL to those of integrin beta subunits from other species revealed that beta OL is a member of the integrin (Itg) beta 1 class. The aa sequence of beta OL shows 78.5-97.9% similarity to beta 1 chains from four other species and displays all the features characteristic of the Itg beta subunits, indicating the high degree of structural conservation seen in this subunit of the Itg receptors.