Comparison of the R-β-actin and Ac-β-actin structures. (A) Ribbon diagram comparing the structure of R-β-actin presented here (cyan) with the previously published structure of human Ac-β-actin (magenta). (B) Close-up view comparing the structure of the active site of R-β-actin with human filamentous Ac-β-actin. (C) Close-up view comparing the N-terminal sections of R-β-actin to that of human filamentous Ac-β-actin.