cupinlike

Cupin-like refers to proteins or protein domains that adopt the cupin fold, a compact beta-barrel (jelly-roll) structure found in the cupin superfamily. The term is used for proteins that contain cupin-like domains but may not display the classical cupin enzymatic activity associated with the canonical family.

Cupin-like domains typically consist of about 110–140 amino acids and can occur as single or duplicated modules within a protein. They often contain conserved sequence motifs implicated in metal binding in many cupins, and many cupin proteins function as metalloenzymes with a dinuclear metal center coordinated by histidines and carboxylate residues. However, some cupin-like proteins operate without metal ions or utilize alternative cofactors, illustrating the versatility of the fold.

The cupin superfamily is highly diverse, including enzymes such as isomerases, dioxygenases, and hydrolases, as well as non-enzymatic binding proteins. Plant germin-like proteins and oxalate oxidases are well-known cupin family members. Others may serve structural roles or participate in various binding or regulatory functions, reflecting the broad applicability of the cupin-like fold.

Evolution and distribution: the cupin-like fold is found across bacteria, archaea, and eukaryotes, and is considered ancient. Diversification has occurred through gene duplication and domain shuffling, resulting in proteins with differing domain architectures and functions. Many organisms encode multiple cupin-like proteins, contributing to the variety observed in the Cupin superfamily.

See also: Cupin, germin-like proteins, purple acid phosphatases, Pfam Cupin domains. The term cupin-like distinguishes proteins with similar beta-barrel folds from the canonical cupin enzymes, acknowledging structural similarity even when canonical motifs or activities are not present.