In 1509, Papantzin fell seriously ill and became comatose. Believing her dead, the Texcocoans laid her in a tomb (unlike the Aztecs who burned their dead), but almost immediately, the mourners heard her cry out to be released. She related a vision, in which a luminous being with "crossed sticks" on his forehead led her to the shore of the Atlantic Ocean, where she saw several large "floating houses" (ships) approach from the horizon, having black crosses on their "wings" (sails) similar to that on her guide's forehead. The princess was informed that the men in the ships came from a distant land and would conquer the Aztecs and bring a knowledge of the One True God. When she related this vision to Moctezuma, he read the doom of his empire in it, and refused to ever speak to her again. Ten years later, the Spanish conquered Mexico, and Papantzin became one of the first natives to convert to Christianity. She was baptized in 1525 when the first Franciscan friars evangelized Texcoco. P-selectin  P-selectin is a protein that in humans is encoded by the SELP gene. P-selectin functions as a cell adhesion molecule (CAM) on the surfaces of activated endothelial cells, which line the inner surface of blood vessels, and activated platelets. In unactivated endothelial cells, it is stored in granules called Weibel-Palade bodies. In unactivated platelets P-selectin is stored in α-granules. Other names for P-selectin include CD62P, Granule Membrane Protein 140 (GMP-140), and Platelet Activation-Dependent Granule to External Membrane Protein (PADGEM). It was first identified in endothelial cells in 1989. P-selectin is located on chromosome 1q21-q24, spans > 50 kb and contains 17 exons in humans. P-selectin is constitutively expressed in megakaryocytes (the precursor of platelets) and endothelial cells. P-selectin expression is induced by two distinct mechanisms. First, P-selectin is synthesized by megakaryocytes and endothelial cells, where it is sorted into the membranes of secretory granules. When megakaryocytes and endothelial cells are activated by agonists such as thrombin, P-selectin is rapidly translocated to the plasma membrane from granules.