Fig. 4.

Recombinant regulator of G protein signaling-21 (RGS21) interacts with Gα in a nucleotide dependent manner. COS7 cells were separately transfected with DNA encoding one of the indicated Gα subunits fused to the KT3 epitope. Cells were lysed in buffer containing GDP, Mg²⁺, and AlF₄⁻ (AMF) or guanine diphosphate (GDP) alone. Cell lysates, His₆-RGS21, and NTA-agarose were incubated overnight prior to washing. Precipitated proteins were heat denatured prior to resolution by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), transferred to a nitrocellulose membrane, and detected using anti-KT3 antibody and chemiluminescence.