Amino Acid Sequence
The specific order in which amino acids are arranged in a peptide or protein chain, read from the N-terminus to the C-terminus. The amino acid sequence determines the molecule's three-dimensional structure, biological activity, and receptor interactions. Even a single substitution can dramatically alter a peptide's properties.
Technical Context
Sequences are written from N-terminus to C-terminus using standard one-letter (e.g. HAEGTFTSDVSSYLEGQAAKEFIAWLVKGR for semaglutide's core) or three-letter codes (e.g. His-Ala-Glu-...). Even a single amino acid substitution can dramatically alter function — semaglutide differs from native GLP-1 at positions 8 (Aib substitution for DPP-4 resistance) and 34 (Arg to Arg with C-18 fatty diacid for albumin binding), extending half-life from 2 minutes to approximately one week. Sequence information is deposited in databases such as UniProt and is critical for understanding the relationship between natural peptides and their synthetic analogues.