CRP1 stabilizes the interaction of α-actinin with actin bundles. Actin filaments were bundled by incubation with α-actinin for 30 min. at room temperature. CRP1 was then added, incubated for an addition 30 min., and centrifuged at 10,000 × g. Proteins from the supernatant (S) and the pellet (P) were separated by electrophoresis and detected by Gelcode Blue staining (A). The percentage of total α-actinin in the pellet was quantified as described in Experimental Procedures (B). n = 3 ± SEM.