Iron-sulfur clusters synthesis

Probably involved with NifS in iron-sulfur cluster synthesis Possibly accelerate MoFe protein maturation Unknown function... 

E. coli uses nitrate as a terminal electron acceptor through a respiratory, dissimilatory nitrate reductase whose synthesis is induced when nitrate is provided, and which is repressed by oxygen. Nitrate reductase is discussed with other molybdoenzymes in Section 62.1.9, and catalyzes the reduction of nitrate to nitrite. The enzyme is isolated from the cytoplasmic membrane of E. coli, and contains three subunits (a, j8 and y) although the y-subunit may be absent in some preparations. The -y-subunit is a b-type cytochrome, and the a-subunit is reported to be the catalytic subunit. The enzyme contains a number of iron-sulfur clusters, including a HiPIP and at least two ferredoxins.1054,1437... 

Zuo, J.L., H.C. Zhou, and R.H. Holm. 2003. Vanadium-iron-sulfur clusters containing the cubane-type [VFejSJ core unit Synthesis of a cluster with the topology of the PN cluster of nitrogenase. Inorg. Chem. 42 4624—4631. 

You JF, Snyder BS, Papaefthymiou GC, Holm RH. On the molecular/solid state boundary. A cyclic iron-sulfur cluster of nuclearity of eighteen synthesis, structure and properties. 

Much of our recent knowledge of the active centers of iron-sulfur proteins has come from the synthesis work of Holm (4) on analog compounds with 4Fe-4S, 2Fe-2S, and IFe centers. The additional ability to extract the iron-sulfur clusters from the proteins themselves and reinsertion of these clusters into other proteins has led to some interesting experiments which, among others, have shown that the 4Fe-4S configuration is more stable than the 2Fe-2S configuration. 

The thiazole ring is synthesized from a pentulose or deoxypentulose 5-phosphate and either glycine or tryptophan, depending on the organism. Incorporation of sulfur leads to formation of hydroxymethyl thiazole, which is then phosphorylated. The sulfur comes from cysteine and is incorporated by formation of a thiocarboxylate at the carboxyl terminal of the enzyme, unlike biotin synthesis (Section 11.1.1), where an iron-sulfur cluster at the active site of the enzyme is the donor. 

It is possibly incorrect to consider biotin synthase an enzyme in the true sense of the word it has a turnover number of 1. It only catalyzes the synthesis of a single molecule of biotin from dethiohiotin before being inactivated. This is because the iron-sulfur cluster of the protein is the source of the sulfur that is incorporated into biotin. There is some evidence that the enzyme can be reactivated by incorporation of sulfur from cysteine, but in vitro addition of the enzymes believed to catalyze this reaction has no effect on the turnover number of the enzyme (Frey, 2001 Marquet et al., 2001). 

Iron sulfur clusters appear in a great many proteins as both electron-transport and enzymatic sites see Iron-Sulfur Proteins), for this reason there has been great interest for 30 years in the development and nnderstanding of iron-snlfur model complexes. Both stmctnre and properties of synthetic analogs of 1-, 2-, 3-, and 4-iron protein active sites have been stndied extensively. This article will address the stmctnral and chemical properties, synthesis, and catalytic activity of these synthetic analogs, as compared to the native protein-bound iron-sulfur cores. 

Similar to E. coli, yeast down-regulate the transcription of non-essential proteins that require iron for activity when the cells become depleted of iron. BI02 and GLTl encode iron-sulfur cluster proteins that are involved in the synthesis... 

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