Chaperones overview

Fig. 1. Schematic overview of copper trafficking and homeostasis inside the yeast cell. The actions of Mad and Ace 1, copper-dependent metalloregulatory transcription factors, control the production of copper import [copper transporter (Ctr) and reductase (Fre)] and detoxification/sequestration [metallothionein (MT)] machineries, respectively. Three chaperone-mediated delivery pathways are shown. Atxl shuttles Cu(I) to the secretory pathway P-type ATPase Ccc2 (right). CCS delivers Cu(I) to the cytoplasmic enzyme copper-zinc superoxide dismutase (SOD) (left). Coxl7 shuttles Cu(I) to cytochrome c oxidase (CCO) in the mitochondria (bottom). Mitochondrial proteins Scol and Sco2 may also play a role in copper delivery to the CuA and CuB sites of CCO. Copper metabolism and iron metabolism are linked through the actions of Fet3, a copper-containing ferroxidase required to bring iron into the cell (lower right) (see text).

Endosialidases contain an intramolecular C-terminal chaperone domain (CTD). This part is required for proper folding of the catalytic part and shares sequence similarities with the C-terminal parts of a variety of tailspike and fiber proteins which have been identified to share a similar chaperone function [112] for an overview of further similar proteins see Schulz et al. [109]. The intramolecular chaperone domain is proteolytic ally released after completion of its job and will be described in Sect. 9. 

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