Mutational analysis of the structure and function of GTP-binding proteins.

Structural, biochemical and molecular genetic studies of EF-Tu, p21ras and alpha s have begun to reveal the inner workings of the molecular machine used by these and other GTP-binding proteins. Further understanding of this molecular machine will ultimately come from crystal structures of the G protein alpha chains as well as from crystal structures of the GTP-bound forms of p21ras and EF-Tu. Mutational analysis will continue to add meaning to the static pictures provided by these crystal structures. Aside from their intrinsic biological interest, other reasons motivate our exploration of the GTP-dependent molecular machine used by GTP-binding proteins. Mutations or bacterial toxins cause disease by inhibiting the GTPase function of p21ras and alpha s. Other G protein alpha chains carry signals that regulate important cell functions, including proliferation. Malfunctions of these other G proteins are highly likely to cause disease. Applying our knowledge of p21ras and alpha s to these additional proteins may turn out to have significant practical consequences.