Protein degradation systems defects

Proteins that are defective or destined for rapid turnover are often marked for destruction by ubiquitination—the attachment of a small, highly conserved protein, called ubiquitin (see p. 244). Proteins marked in this way are rapidly degraded by a cellular com ponent known as the "proteasome", which is a complex, ATP-dependent, proteolytic system located in the cytosol. 

Defective proteins and those with characteristically short half-lives are generally degraded in both bacterial and eukaryotic cells by selective ATP-dependent cytosolic systems. A second system in vertebrates, operating in lysosomes, recycles the amino acids of membrane proteins, extracellular proteins, and proteins with characteristically long half-lives. 

Since iron is involved in many central nervous system processes that could affect infant behaviour and development, iron deficiency has adverse effects on brain development, both pre- and post-natal. In various epidemiological studies, it is reported that children with iron-deficiency anaemia have poorer performances on tests of some specific cognitive function. Animal experiments have identified some of the defects of reduced iron availability on brain function, which include post-translational changes (which result in a failure of iron incorporation into protein structures which are subsequently degraded), vulnerability of the developing hippocampus (with loss of the neuronal metabolic marker cytochrome c oxidase), and altered dendritic stmcture. Iron deficiency will also have a direct effect on myelin, including a decrease in myelin lipids and proteins, as well as neurotransmitter systems, since iron... 

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