Formation of a cyclic sulfenyl amide residue at the active site of redox-regulated proteins has been proposed as a protection mechanism against irreversible oxidation as the sulfenyl amide intermediate has been identified in several proteins.

In this work we have also identified two PFAM families, Glutamine amidotransferase and Carbon-ni-trogen hydrolase, that lack experimental evidence of cysteine oxidation but have a relevant Cys in the active site .

On the other hand, pth has an extra domain called “lid domain” which acts as a gate to the active site of this enzyme, protecting it from oxidative stress.

Because of its pathological relevance and protective role in oxidative stress DI-l has been intensively studied and oxidation of the active site cysteine has been described several times [78,85].

Proteins that have a reactive cysteine in their active site that has a low pKa are susceptible to inactivation by radical species like H202.

By combining this information with protein structure information, we found that all (10 out of 10) such identified hotspots, where they fell within known oncoproteins, are ‘functional hotspots’ in the sense that all fell within ligand-binding or active sites .

For oncoproteins, of 40 mutational hotspots, 15 (38%) fell at functional sites, including GTP/ ATP binding sites and other active sites of enzymes.

Here, we collectively analyzed the domain position-based hotspots for K-RAS, H-RAS, and N-RAS, finding that at least one of the GTP binding site residues p.G12 or p.G13, or the active site residue p.R61 show a relatively high mutation rate in at least five cancer types (Fig.