In addition to fucosylation of NOTCH receptor precursors, glucosylation represents another crucial NOTCH processing reaction, required for full receptor function. Endoplasmic reticulum O-glucosyl transferase, POGLUT1, adds a glucosyl group to conserved serine residues within the EGF repeats of NOTCH. The consensus sequence of POGLUT1 glucosylation sites is C1-X-S-X-P-C2, where C1 and C2 are the first and second cysteine residue in the EGF repeat, respectively, while X represents any amino acid. Only those glucosylation sites that are conserved between human, mouse and rat isoforms are shown. In human NOTCH1, the consensus glucosylation site on serine at position 951 was not annotated since it is not conserved in rat NOTCH1. In human NOTCH4, glucosylation at serine 398 was not annotated because this site is not conserved in rat, and glucosylation at serine 936 was not annotated because this site is not conserved in mouse. Glucosylation of NOTCH4 serine 773 was not annotated because a proline at position 775 is not conserved in either mouse or rat.