Properties of the M Antigen Solubilized from Genetically High Potassium Sheep Red Cells

Abstract

The M antigen genetically associated with the high potassium (HK) status of sheep red cells was solubilized in 0.5% Triton X-100. This procedure did not impair M-antibody binding in the presence of detergent because solubilized membranes bound M-antibody in units equivalent to control membranes. As judged by M-antibody binding, the antigen was found to be stable in 0.5% Triton X-100 at 4°C but lost its activity rapidly at 37°C or when diluted to low detergent concentrations. However, the formation of the M antigen-antibody complex prior to dilution or exposure to elevated temperature protected the M antigen from inactivation. Brief exposure to alkaline pH released the extrinsic membrane proteins from red cell membranes without solubilizing the M antigen. The intrinsic membrane proteins were further separated by ion exchange chromatography on Affi-Gel 102. M antigenic activity copurified with the sheep specific protein band 2.2, band 6, and the glycoproteins and appeared to be separate from the main portion of band 3 protein.

Key Words:

• sheep red cells
• M antigen
• band 3 protein