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The two thioether linkages are typically made by cysteine residues of the protein. These linkages do not allow the heme C to easily dissociate from the holoprotein , cytochrome c , compared with the more easily dissociated heme B that may dissociate from the holoprotein, the heme-protein complex, even under mild conditions.
The CHAP domain is found in a wide range of protein architectures; it is commonly associated with bacterial type SH3 domains and with several families of amidase domains. It has been suggested that CHAP domain containing proteins utilise a catalytic cysteine residue in a nucleophilic-attack mechanism. [1] [2]
Cysteine has l chirality in the older d / l notation based on homology to d - and l-glyceraldehyde. In the newer R / S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, cysteine (and selenocysteine) have R chirality, because of the presence of sulfur (or selenium) as a second neighbor to the ...
Oxidative pathway in Gram-negative bacteria. The oxidative pathway relies, just like the isomerization pathway, on a protein relay. The first member of this protein relay is a small periplasmic protein (21 kDa) called DsbA, which has two cysteine residues that must be oxidized for it to be active.
Glutamate racemase is known to use its active site to undergo racemization and participate in the cell wall biosynthesis pathway of bacteria. [2] Based on homology to other racemases and epimerases, glutamate racemase is thought to employ two active site cysteine residues as acid/base catalysts. [7]
Bacterial-type ferredoxins may in turn be subdivided into further groups, based on their sequence properties. Most contain at least one conserved domain, including four cysteine residues that bind to a [Fe 4 S 4] cluster. In Pyrococcus furiosus Fe 4 S 4 ferredoxin, one of the conserved Cys residues is substituted with aspartic acid.
Caspase-3 shares many of the typical characteristics common to all currently-known caspases. For example, its active site contains a cysteine residue (Cys-163) and histidine residue (His-121) that stabilize the peptide bond cleavage of a protein sequence to the carboxy-terminal side of an aspartic acid when it is part of a particular 4-amino acid sequence.
Zinc and Cadmium are tetrahedrally coordinated to cysteine residues, and each metallothionein protein molecule may bind up to 7 atoms of Zn or Cd. [5] The biosynthesis of metallothionein appears to increase several-fold during periods of oxidative stress to shield the cells against cytotoxicity and DNA damage.