The protein encoded by EAG_12734 mediates the addition of adenosine 5'-monophosphate (AMP) to specific residues of target proteins. Adenylyltransferase activity is inhibited by the inhibitory helix present at the N-terminus. The protein is the integral component of membrane and is involved in basic cell processes including histamine transport, protein adenylylation, visual behavior and detection of light stimulus involved in visual perception.