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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]
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 cysteine sulfhydryl group is nucleophilic and easily oxidized. The reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pK a values close to neutrality, so are often in their reactive thiolate form in the cell. [23] Because of its high reactivity, the sulfhydryl group of cysteine has numerous biological ...
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.
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.
The active site of MerA consists of four cysteine residues, a FAD, and a tyrosine residue. When bound to a Hg 2+, a complex is formed with at least two cysteine thiolates at any time until release. [4] Two cysteine residues (Cys-136 and Cys-141) are buried within the protein and the other two cysteine residues (Cys-558' and Cys-559') are found ...
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.
The synthesis of O-acetylserine is catalyzed by serine acetyltransferase and together with O-acetylserine (thiol)lyase it is associated as enzyme complex named cysteine synthase. The formation of cysteine is the direct coupling step between sulfur (sulfur metabolism) and nitrogen assimilation in plants.