N-glycosylated residue modified L-histidine residue alpha-N-gluconoylated L-histidine 179.0555572509765625 179.149993896484375 316.114471435546875 316.290008544921875 MOD:01085 natural C 6 H 11 O 6 N-term C 12 H 18 N 3 O 7 Occurs on His-tagged proteins expresssed in E. coli. From DeltaMass: Average Mass: 178 Formula: C6H10O6 Monoisotopic Mass Change: 178.05 Average Mass Change: 178.14 References: Geoghegan, K. F., H. B. Dixon, et al. (1999). Spontaneous alpha-N-6-phosphogluconoylation of a His tag in Escherichia coli: the cause of extra mass of 258 or 178 Da in fusion proteins. Anal Biochem 267(1): 169-84. Mass listed here is 179 because it's N-terminal. A protein modification that effectively replaces the N-terminal hydrogen atom of a N-terminal histidine residue with a gluconoyl group linked through a glycosidic bond. modification from DeltaMass H PSI-MOD