Cys2Cys2

Cys2Cys2 refers to a protein structural motif characterized by the presence of two cysteine amino acid residues that are covalently linked by a disulfide bond. This disulfide bond forms between the thiol (-SH) groups of the two cysteine side chains, resulting in a cyclic structure within the polypeptide chain. This motif is a specific type of disulfide bridge, which is a common post-translational modification found in many proteins.

The formation of a Cys2Cys2 motif plays a crucial role in stabilizing protein structure and function. The disulfide bond introduces rigidity and can dictate the three-dimensional folding of a protein by holding different parts of the polypeptide chain together. This structural integrity is often essential for the protein to perform its biological role, whether it be enzymatic activity, binding to other molecules, or structural support.

Proteins containing Cys2Cys2 motifs are found across a wide range of organisms and protein families. Examples include many secreted proteins, extracellular matrix proteins, and proteins involved in redox regulation. The redox environment of the cell or extracellular space influences the formation and breakage of these disulfide bonds, allowing for dynamic regulation of protein structure and activity. The precise location and number of such motifs within a protein can vary, contributing to the diversity of protein structures and functions.