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H-Ras is a protypical example of a small G protein which binds GTP and which
has GTPase activity. This signaling is active in the GTP bound state, and
inactive in the GDP bound state.
For more information see
Biochemistry Online: Chapter 9C-7 - Small G proteins, GAPs and GEFs
II. General Structure
The superfamily of small G proteins have a common 20K molecular weight
catalytic domain with 5 alpha helices, 6 beta strands and connecting loops.
The G1 loop binds phosphate groups as is often called the P-loop (as in the
case of protein tyrosine phosphatases). Its binds GTP and GDP and has
GTPase activity. The small G proteins are "active" in the GTP bound
form. Hydrolysis of GTP to GDP causes the protein to become inactive in
calculate molecular surface (slow)
display jvxl premade molecular surface