Model of the Human P2X1 Receptor (IMAGE) University of Leicester Caption This is the model of the human P2X1 receptor for ATP,. The three subunits that make up the functional receptor are shown in red, white and blue. Credit University of Leicester Usage Restrictions Use only with credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.