Identification of residues in the nucleotide binding site of the epidermal growth factor receptor/kinase

We have purified the epidermal growth factor receptor/kinase from A431 membrane vesicles which had been affinity labeled with the ATP analog, 5'-p-fluorosulfonylbenzoyl[8-¹⁴C]adenosine. The resulting purified, affinity labeled receptor/kinase preparation has been subjected to reduction and carboxymethylation followed by tryptic digestion. From this digest, we have isolated and sequenced the tryptic peptide containing the major site of labeling by the ATP analog. The sequence of this peptide is Ile-Pro-Val-Ala-Ile-X-Glu-Leu, where X corresponds to Lys 721 of the derived sequence of the EGF receptor/kinase.