One known as integrates. Let's suppose that's the blue one, that's the green one, and the other one is known as reverse transcriptase. Let's suppose that is our blue one and we'll discuss what their function is in just a moment. So basically, the GP 120 glycoprotein of HIV binds to a specific glycoprotein receptor found on membrane of immune cells. And this special type of glycoprotein is called CD four glycoprotein. So HIV contains a glycoprotein, the GP 120, that can bind onto the CD four protein of immune cells are white blood cells.