Ferredoxinlike

Ferredoxinlike, or ferredoxin-like, refers to a protein domain or set of domains that adopt the ferredoxin-like fold. This fold is a compact, beta-sheet–rich scaffold that serves as a versatile platform for electron transfer and metal binding. The term is used mainly in structural and bioinformatic contexts to denote topology rather than a single enzymatic activity.

Structure and cofactors: Typical ferredoxin-like domains are small, about 60–120 amino acids, and can occur as standalone modules or as subdomains within larger proteins. The core consists of a beta-sheet with an alpha-helix. In many ferredoxin-like domains a [4Fe-4S] cluster is coordinated by conserved cysteine residues, enabling electron transfer. Others bind different metal ions such as zinc or function without a metal cofactor, serving alternative roles such as ligand binding or scaffolding.

Distribution and function: They are widespread in bacteria, archaea, and eukaryotes and appear in proteins involved in photosynthesis, respiration, nitrogen fixation, and various redox pathways. In photosynthetic organisms, ferredoxin itself is a key electron carrier, while ferredoxin-like domains are found in reductases, oxidoreductases, and radical SAM enzymes, contributing to electron transfer or radical generation. Not all ferredoxin-like domains carry iron-sulfur clusters; some serve structural roles or regulate interactions within larger proteins.

Classification and terminology: In databases such as Pfam and CATH, ferredoxin-like denotes a superfamily of domains sharing the common ferredoxin-like topology. The term emphasizes structural similarity rather than a specific function of authentic ferredoxins. See also ferredoxin, iron-sulfur clusters, radical SAM, and electron transfer.