High-potential iron proteins cluster stability

High-potential iron proteins, 45 313-314, 344 cluster stability, 45 324-332 function, 45 315-316 residues, 45 322-344 structure and, 45 317-322 redox properties, 45 333-344 solvent accessibility, 45 330, 332-333 source and function, 45 314-316 structure, 45 316-322 hydrogen bonding and, 45 321-322 intermolecular aggregation, 45 322 primary, 45 317-318 secondary and tertiary, 45 318-321... 

High-potential iron proteins (HiPIPs) comprise a subset of the 4Fe-4S cluster family of metalloproteins that are characterized by a positive reduction potential, F , in the range of +50 to +450 mV. This class is differentiated from the 4Fe-4S centers in low-potential ferredoxins, which show a negative E, tjrpically varying between -100 and -650 mV. The origin of these distinct redox properties has been rationalized in terms of the three-state hypothesis of Carter (1), summarized in Scheme 1, and can be attributed to the stability of the common [Fe4S4(SR)4] state. 

FIGURE 16 Ribbon representation of irregular structures (a) High potential iron-sulfur protein coordinated to a 4Fe-4S cluster, (b) RAG1 DMA binding protein which contains representative examples of Zn-tinger domains, (c) Defensin as example of a membrane toxin stabilized by disulfide bonds, and (d) Chinese bird spider neurotoxin which contains a cystine knot. 

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