Walter Gilbert and Benno Müller-Hill were the first to successfully identify it, using a different technique. However, Arthur Riggs was the first to purify usable quantities of a transcription factor protein, the lac repressor.
Walter Gilbert and Benno Müller-Hill were initially successful in identifying it through a different method. In contrast, Arthur Riggs was the first to purify enough quantities of a transcription factor protein, specifically the lac repressor.