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Isolation and characterization of recombinant eel growth hormone expressed in Escherichia coli
S Sugimoto1, K Yamaguchi, Y Yokoo
1Tokyo Research Laboratories, Kyowa Hakko Kogyo Co., Ltd., Japan.
Abstract:
To obtain information about the microheterogeneity of recombinant protein, recombinant eel growth hormone II (EGH) analogues expressed in Escherichia coli were isolated and characterized. The modification was classified into three types: monodeamidation of Asn, oxidation of Met and N-terminal formylation. Monodeamidated EGH was isolated by ion-exchange chromatography. The major deamidation site (Asn 147) was determined by peptide mapping using the substrate specificity of trypsin. Oxidized EGH and N-terminal-formylated EGH were isolated by reversed-phase high-performance liquid chromatography. Oxidized EGH was identified by amino acid composition analysis and N-terminal-formylated peptide by mass spectrometry.