Cystine
Cystine is the oxidized derivative of the amino acid cysteine and has the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is poorly soluble in water. As a residue in proteins, cystine serves two functions: a site of redox reactions and a mechanical linkage that allows proteins to retain their three-dimensional structure. Formation and reactions Structure Cystine is the disulfide derived from the amino acid cysteine. The conversion can be viewed as an oxidation: : Cystine contains a disulfide bond, two amine groups, and two carboxylic acid groups. As for other amino acids, the amine and carboxylic acid groups exist is rapid equilibrium with the ammonium-carboxylate tautomer. The great majority of the literature concerns the ''l,l-''cystine, derived from ''l''-cysteine. Other isomers include ''d,d''-cystine and the meso isomer d,l-cystine, neither of which is biologically significant. Occurrence Cystine is common in many foods such as eggs, meat, dairy products, and w ...
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SLC7A11
Cystine/glutamate transporter is an antiporter that in humans is encoded by the ''SLC7A11'' gene. The SLC7A11 gene codes for a sodium-independent cystine-glutamate antiporter that is chloride dependent, known as system Xc- or xCT. It regulates synaptic activity by stimulating extrasynaptic receptors and performs nonvesicular glutamate release. This gene is highly expressed by astrocytes and couples the uptake of one molecule of cystine with the release of one molecule of glutamate. The dimer cystine gets taken up by glial cells and the monomer of cystine, cysteine, is taken up by neurons. The expression of Xc- was detected throughout the brain with higher expression found in the basolateral amygdala, the Retina and the prefrontal cortex. The inhibition of system Xc- has been found to alter a number of behaviors, which suggests that it plays a key role in excitatory signaling. Structure SLC7A11 is a member of a