SDS-PAGE of mouse RBC membrane proteins showing the absence of immunoreactive protein 7.2b in homozygous 7.2b knock-out mouse RBC. Lane 1, control mouse; lane 2, homozygous 7.2b knock-out mouse. (A) SDS-PAGE gel stained with coomassie blue. A 30-kD band is seen in both wild-type and 7.2b knock-out mouse samples, reflecting the presence of several non-7.2b RBC membrane proteins normally found in this region.2 (B) Immunoblot of SDS-PAGE gel prepared with affinity-purified rabbit polyclonal antihuman protein 7.2b antibody. (C) Immunoblot of SDS-PAGE gel prepared with monoclonal murine antimouse protein 7.2b antibody. Immunoreactive 7.2b is absent from the RBC membranes of the knock-out mouse.