C-terminal sequence analysis
The ability to sequence the C-terminal region of a protein forms a critical part of a protein characterization package. C-terminal microheterogeneity frequently arises as a post translational modification, hence identification of the C-terminus and any truncated versions or 'ragged ends' is key in assessing the 'intactness' of a protein biopharmaceutical.
Unlike N-terminal sequencing, there is no fully reliable automated instrumental technique available. Confirmation of C-terminal sequence can usually be achieved using a combination of peptide mapping strategies and ES-MS/MS sequencing, combined with enzymic digestions and/or molecular weight analysis. Experience enables SGS M-Scan to choose the most appropriate methods, which will vary on according to factors such as peptide or protein size, glycosylation state and the theoretical C-terminal amino acid sequence.
C-terminal sequence analysis is a key part of the ICH Q6B guidelines for characterization and confirmation of biopharmaceuticals in support of new marketing applications.