Homologies in the primary structure of GTP-binding proteins: the nucleotide-binding site of EF-Tu and p21.

An examination of the available amino acid sequences of GTP-binding proteins has revealed that each contains a polypeptide essentially homologous for all of them. These sequences for elongation factor-Tu (EF-Tu) and the human bladder protein p21 exhibit a singular degree of homology (50%). Chemical and structural evidence indicates that this sequence in EF-Tu constitutes part of the nucleotide-binding site. The homologous sequences may therefore contribute to the GTP-binding sites of the other proteins.