https://www.ncbi.nlm.nih.gov/Structure/pdb/1CIP
1CIP: GI-ALPHA-1 SUBUNIT OF GUANINE NUCLEOTIDE-BINDING PROTEIN COMPLEXED WITH A GTP ANALOGUE
PROTEIN (GUANINE NUCLEOTIDE-BINDING PROTEIN ALPHA-1 SUBUNIT)MAGNESIUM IONPHOSPHOAMINOPHOSPHONIC ACID-GUANYLATE ESTER