Iron metalloproteins

We have chosen here a classification of iron metalloproteins based on the coordination chemistry of the metal. This enables us to more easily appreciate the diversity of biochemical... 

Whitwam, R.E. Ahlert, J. Holman, T.R. Ruppen, M. Thorson, J.S. (2000) The gene calC encodes for a non-heme iron metalloprotein responsible for calicheamicin self-resistance in Micromonospora. J. Am. Chem. Soc., 122,1556-7. 

FIGURE 10.25 Utilization of transferrin and its receptor for delivering iron into the cell. The iron/transferrin complex circulates throughout the bloodstream. Eventually, the iron/transferrin complex binds to the transferrin receptor, a membrane-bound protein (Step 1). Part of the plasma membrane pinches off, creating an endocytotic vesicle, which resides in the cytoplasm (Step 2). The interior of the vesicles becomes acidified (Step 3), and the iron atoms leave the vesicle (Step 4). MobUferrin is a cytosolic protein that is thought to bind the released iron atoms, and to shuttle them to newly synthesized iron metalloproteins (Conrad et al, 1996). Finally, the transferrin receptor is inserted back into the plasma membrane (Steps 5 and 6). 

Dinuclear iron metalloproteins have a diversity of functions in nature, i.e. reversible 02-binding (hemerythiin), DNA synthesis (ribonucleotide reductase) and alkane... 

Frieden E (1976) Copper and iron metalloprotein. Trend Biochem Sci 1 273-274... 

A second iron metalloprotein that is larger (about 220.000 Daltons) and also eventually contains another transition metal that is different for the three kinds of nitrogenase enzymes Mo (MoFe protein), V (VFe protein) or Fe (FeFe protein). It is the MoFe protein that is tiie best known. It contains ... 

Metalloproteins contain metal atoms Ferritin Iron 35... 

HEMOPROTEINS. These proteins are actually a subclass of metalloproteins because their prosthetic group is heme, the name given to iron protoporphyrin IX (Figure 5.15). Because heme-containing proteins enjoy so many prominent biological functions, they are considered a class by themselves. 

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

Injury to cells and tissues may enhance the toxicity of the active oxygen species by releasing intracellular transition metal ions (such as iron) into the surrounding tissue from storage sites, decompartmentalized haem proteins, or metalloproteins by interaction with delocalized proteases or oxidants. Such delocalized iron and haem proteins have the capacity to decompose peroxide to peroxyl and alkoxyl radicals, exacerbating the initial lesion. 

FIGURE 3.10 EPR of ferricyanide. Potassium ferricyanide is a general-purpose oxidant of metalloproteins. The low-spin 3c/5 Fe(III) of frozen dissolved K3Fe(CN)6 gives a broad 5=1/2 spectrum with main peak at g = 2.68 (v = 9407 MHz T = 15.5 K). The sharper feature around g = 2 is from an iron-sulfur cluster anaerobically oxidized in this experiment by ferricyanide to the [3Fe-4S]1+ form with S = 1/2. 

SOD comprises a family of metalloproteins primarily classified into four groups copper, zinc-containing SOD (Cu, Zn-SOD), manganese-containing SOD (Mn-SOD), iron-containing SOD (Fe-SOD) and nickel-containing SOD (Ni-SOD). In the following studies, we will only focus on the uses of the former three kinds of SODs to construct SOD-based 02 biosensors since the last one, Ni-SOD, is not commercially available. 

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