DOI 10.1007/s10254-004-0034-4

Abstract C3-like exoenzymes comprise a family of seven bacterial ADP-ribosyltrans-ferases, which selectively modify RhoA, B, and C at asparagine-41. Crystal structures of C3 exoenzymes are available, allowing novel insights into the structure-function relation-ships of these exoenzymes. Because ADP-ribosylation specifically inhibits the biological functions of the low-molecular mass GTPases, C3 exoenzymes are established pharmaco-logical tools to study the cellular functions of Rho GTPases. Recent studies, however, in-dicate that the functional consequences of C3-induced ADP-ribosylation are more com-plex than previously suggested. In the present review the basic properties of C3 exoen-zymes are briefly summarized and new findings are reviewed