Asp102

Asp102 is a designation used in protein science to refer to the aspartic acid residue located at position 102 in a given reference sequence or structure. The exact residue at position 102 can vary between proteins, because numbering depends on the reference sequence used. Consequently, Asp102 in one protein does not imply the same absolute position or function in another protein.

A well-known context for Asp102 is its role in the catalytic triad of serine proteases in the chymotrypsin family. In these enzymes, Asp102, together with His57 and Ser195, participates in a charge-relay system that facilitates catalysis. The aspartate side chain helps orient and stabilize the histidine, enabling efficient proton transfer during substrate turnover. Mutations at Asp102 in such enzymes often lead to substantial loss of catalytic activity, underscoring its functional importance in that family.

Beyond serine proteases, Asp102 can fulfill other roles in proteins depending on the structural and chemical environment. It may participate in coordinating metal ions, forming salt bridges that help stabilize specific folds, or contributing to substrate binding and electrostatic interactions within active or binding sites. The precise function of Asp102 is therefore context-dependent and must be inferred from the protein’s sequence, structure, and biochemical data.

In practice, researchers refer to Asp102 with attention to the reference sequence and numbering scheme used (uniprot, PDB, or crystal structure numbering). When comparing proteins, alignment is necessary to map Asp102 accurately across different contexts.