Eventually, this cross-link between the two proteins is broken by a nucleophilic attack of the second cystein residue in the DsbA active site.

All TIMPs contain twelve conserved cystein residues, which form six disulfide bonds.

The taste modifying protein, miraculin, has seven cystein residues in a molecule composed of 191 amino acid residues.

In 1994, Robertson et al. noted that the amastigotes of L. mexicana have a higher activity of cystein proteases compared to its promastigote forms.

TTD can be diagnosed by the presence of tigertail-striped patterns in hair visible under polarised light microscopy, or biochemically by a reduced cystein content of the hairs.

J. Martens, H. Offermanns, P. Scherberich: Synthese von racemischem Cystein, in: Angew.

They share and extracellular domain, which contains N-terminal domain rich in cystein, F2 fibronectin type II domain and several C-lectin domains.

Formation of a disulfide bond between two cystein residues within the protein closes the hydrophobic funnel of the catalyic site, and thus acts as an on/off switch for catalytic activity.

This Ero1p protein forms a mixed disulfide with PDI, which is resolved by a nucleophilic attack of the second cystein residue in one of the active sites of PDI.

The histidine molecule is protonated by the cysteine residue and this allows the cystein residue to undergo a nucleophillic attack on the isopeptide bond, which removes the ubiquitin from the substrate protein.

Research is being done to develop a vaccine against the promastigotes, although the work by Roberts may shed light into developing a vaccine or agent that targets the cystein proteases and other enzymes that are found in abundance in the amastigotes.

Jain et al. (2011) indicated that silver nanoparticle synthesis for A. flavus occurs initially by a reductase followed by a protein (cystein and free amine groups) electrostatic attraction which stabilizes the nanoparticle by forming a capping agent.

Moreover, regucalcin has been shown to have an inhibitory effect on aminoacyl t-RNA synthetase, a rate limiting enzyme at translational process of protein synthesis and an activatory effect on cystein protease and superoxide dismutase in liver and kidney cells.