N-glycosylated residue modified L-histidine residue alpha-N-6-phosphogluconoylated L-histidine 259.021881103515625 259.1199951171875 396.080810546875 396.269989013671875 A protein modification that effectively replaces the N-terminal hydrogen atom of a N-terminal histidine residue with a 6-phosphogluconoyl group linked through a glycosidic bond. modification from DeltaMass C 12 H 19 N 3 O 10 P 1 C 6 H 12 O 9 P 1 H MOD:01118 N-term Occurs on His-tagged proteins expresssed in E. coli.From DeltaMass: Average Mass: 258 Formula: C6H10O6HPO3 Monoisotopic Mass Change: 258.01 Average Mass Change: 258.12 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 is one Da higher because this is an N-terminal modification PSI-MOD natural