Task: Text Categorization
Input (English): Notably, one of these entities is absent in the Leishmania mexicana GPI8 protein, and abnormally low numbers of pericytes occur if one is missing from PDGF. Binding of 14-3-3 proteins to GABAB ["Gabba-sub-bee"] receptors does not occur when two arginines are mutated to alanine in one of these entities, which also binds to the COPI complex. They are usually C-terminal signals, and a common mammalian one consists of the amino acids lysine, aspartate, gluatamate, and leucine, or KDEL. hnRNP C proteins contain one of them that allows them to override nuclear export signals. For 10 points, name these signals important in directing proteins to the correct membranes, most often used to prevent a protein's export from the endoplasmic reticulum. 
Output (English): Science