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Identification of a lysine residue at a nucleotide binding site in the firefly luciferase with p-fluorosulfonyl[14C]benzoyl-5'-adenosine.

Firefly luciferase is 80-90% inactivated within 3 h upon incubation with the adenine nucleotide analogue p-fluorosulfonylbenzoyl-5'-adenosine (FSBA). Although 4 mol of 14C-FSBA/mol of enzyme is irreversibly bound during inactivation, only 1 mol of 14C-FSBA appears to be specifically directed to an adenine nucleotide binding site on the enzyme. The other 3 mol of 14C-FSBA is bound to the protein nonspecifically. The major radioactive peptide in a tryptic digest os labeled luciferase was isolated and shown to have the following amino acid sequence: *Lys-Gly-Glx-Asx-Ser-Lys, where *Lys is the radioactive derivative of the lysine residue that was sulfonylated during the inactivation.