sentence: While the first two regions have some unusual properties in rhodopsin , e.g ., a covalently-bound ligand and the binding pocket tightly covered with β - sheet , which makes these data less transferable to other family members , NPxxY motif is very conserved in GPCRs and frequently mentioned in previous sections as a crucial element of molecular switches and signaling pathways , so the observed behavior of functional water molecules in its neighborhood may be considered as a more general pattern .