Cystine bonds are formed in Proinsulin-1 between cysteine residues 31 and 96, cysteine residues 43 and 109, and cysteine residues 95 and 100. Ero1-like alpha does not directly catalyze the oxidation of cysteines to cystine. Instead it maintains a suitably oxidizing environment for the reactions to occur . Though Ero1-like alpha can act via specific isomerases such as P4HB/PDI, there is currently no evidence that formation of cystine bonds in insulin requires a specific isomerase. Interestingly, even in beta cells of wild type animals, trace amounts of incorrectly bonded proinsulin can be detected. Thus, the formation of correct cystine bonds may involve a period of bond shuffling.
Dodson, G, Steiner, D
Qiao, ZS, Min, CY, Hua, QX, Weiss, MA, Feng, YM
Min, CY, Qiao, ZS, Feng, YM
Liu, M, Ramos-Castañeda, J, Arvan, P
Liu, M, Li, Y, Cavener, D, Arvan, P
Chang, SG, Choi, KD, Jang, SH, Shin, HC
disulfide oxidoreductase activity of EROIL-like Proteins [endoplasmic reticulum lumen]
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