Hydrophobic amino acids at the cytoplasmic ends of helices 3 and 6 of rhodopsin conjointly modulate transducin activation

► Hydrophobic amino acid interactions are critical for rhodopsin-G-protein activation. ► The two second and third cytoplasmic loops cooperate for providing a common domain for G-protein recognition. ► Specificity for G-protein activation may require the complete second and third cytoplasmic loops of the receptor.