Cys1Cys4containing

Cys1Cys4-containing is a descriptor used in protein sequence annotation to indicate the presence of a conserved cysteine-based motif in which cysteine residues occupy the first and fourth positions of a tetrapeptide, commonly represented as Cys-X-X-Cys. The X denotes any amino acid.

In many contexts, this motif can participate in redox chemistry via intramolecular disulfide bonds or coordinate metal ions as part of a larger binding site. The presence of cysteines in this arrangement often raises the possibility of redox activity or metal coordination, though the exact function depends on the surrounding sequence and three-dimensional structure.

It is not a stand-alone domain; rather, it is a motif found across diverse protein families. Because it is a short pattern, its functional implications can vary widely, and it may contribute to stability, folding, or catalytic or binding properties within a larger protein context.

Detection and annotation typically rely on pattern searches or multiple sequence alignments that identify Cys-X-X-Cys motifs, sometimes annotated in databases as Cys1Cys4-containing. Caution is warranted: the presence of a Cys1Cys4 motif alone does not define function, and experimental validation is usually required to determine whether a disulfide bond, metal-binding site, or other role is present.

This motif is of interest in studies of redox biology, metalloproteins, and protein folding, where cysteine-based motifs can influence structure and activity.