Rapid isolation of G alpha 13 from bovine brain membranes: supportive effect of ethylene glycol.

G13 belongs to the G12-subfamily of heterotrimeric regulatory G-proteins. Employing specific antibodies, we isolated G alpha 13 from bovine brain by a four-step purification protocol combining conventional and affinity chromatography. The use of ethylene glycol as a protective agent influenced the elution properties of G alpha 13 markedly. Only in the presence of ethylene glycol (30% v/v) a clear separation of G alpha 13 from other G-proteins was achieved during the initial anion exchange chromatography. This allowed isolation of G alpha 13 by subunit exchange chromatography on beta gamma-agarose. G alpha 13 was only released from immobilized beta gamma-dimers via activation by AMF but not by GTP gamma S, pointing to a poor basal nucleotide exchange of this protein. In contrast, N-terminally truncated G alpha 13 did not bind to immobilized beta gamma-dimers.