Pages in category "Metalloproteins"

The following 27 pages are in this category, out of 27 total. This list may not reflect recent changes (learn more).

A

  • Aromatic-ring-hydroxylating dioxygenases
  • Two prosthetic groups, a Rieske-type [Fe2S2] center and a mononuclear iron, are associated with the α-subunit in the (αβ)n-type enzymes. Electron transfer components are composed of flavoprotein (NADH:ferredoxin oxidoreductase) and Rieske-type [Fe2S2] ferredoxin.

C    

 

  • Calmodulin is an example of a signal-transduction protein. It is a small protein that contains four EF-hand motifs, each of which able to bind a Ca2+ ion.In an EF-hand loop the calcium ion is coordinated in a pentagonal bipyramidal configuration. Six glutamic acid and aspartic acid residues involved in the binding are in positions 1, 3, 5, 7 and 9 of the polypeptide chain.
  • Carbonic anhydrase. The structure of the active site in carbonic anhydrases is well-known from a number of crystal structures. It consists of a zinc ion coordinated by three imidazole nitrogen atoms from three histidine units. The fourth coordination site is occupied by a water molecule. The coordination sphere of the zinc ion is approximately tetrahedral.


    Chlorophyll plays a crucial role in photosynthesis. It contains a magnesium enclosed in a chlorin ring. However, the magnesium ion is not directly involved in the photosynthetic function and can be replaced by other divalent ions with little loss of activity. Rather, the photon is absorbed by the chlorin ring, whose electronic structure is well-adapted for this purpose.
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  • The cobalt-containing Vitamin B12 (also known as cobalamin) catalyzes the transfer of methyl (−CH3) groups between two molecules, which involves the breaking of C−C bonds, a process that is energetically expensive in organic reactions. The metal ion lowers the activation energy for the process by forming a transient Co−CH3 bond.[23] The structure of the coenzyme was famously determined by Dorothy Hodgkin and co-workers, for which she received a Nobel Prize in Chemistry.[24] It consists of a cobalt(II) ion coordinated to four nitrogen atoms of a corrin ring and a fifth nitrogen atom from an imidazole group. In the resting state there is a Co−C sigma bond with the 5′ carbon atom of adenosine.[25] This is a naturally occurring organometallic compound, which explains its function in trans-methylation reactions, such as the reaction carried out by methionine synthase.

D

  • Deoxyribozymes, also called DNAzymes or catalytic DNA, are first discovered in 1994 and quickly emerged as a new class of metalloenzymes.[35] Almost all DNAzymes require metal ions for their function; thus they are classified as metalloenzymes. Although ribozymes mostly catalyze cleavage of RNA substrates, variety of reactions can be catalyzed by DNAzymes including RNA/DNA cleavage, RNA/DNA ligation, amino acid phosphorylation and dephosphorylation, and carbon–carbon bond formation.[36] Yet, DNAzymes that catalyze RNA cleavage reaction are the most extensively explored ones. 10-23 DNAzyme, discovered in 1997, is one of the most studied catalytic DNAs with clinical applications as a therapeutic agent.[37] Several metal-specific DNAzymes have been reported including the GR-5 DNAzyme (lead-specific),[38] the CA1-3 DNAzymes (copper-specific), the 39E DNAzyme (uranyl-specific)[39] and the NaA43 DNAzyme (sodium-specific).[40]

F

  • FeMoco
  •  FeMoco is the primary cofactor of nitrogenase. Nitrogenase is the enzyme that catalyzes the conversion of atmospheric N2 into ammonia (NH3), through the process known as nitrogen fixation. Containing iron and https://en.wikipedia.org/wiki/Nif_genemolybdenum, the cofactor is called FeMoco. Its stoichiometry is Fe7MoS9C.

H

  •  
  • Hemovanadin
  •  Bielig HJ, Bayer E, Califano L, Wirth L (1954). "Vanadium-containing blood pigment. 11. Hemovanadin, a sulfate complex of trivalent vanadium". Pubblicazioni della Stazione Zoologica di Napoli. 25: 26–66. OCLC 4344268.
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  •  Hydrogenase
    Main article: Hydrogenase
    Hydrogenases are subclassified into three different types based on the active site metal content: iron–iron hydrogenase, nickel–iron hydrogenase, and iron hydrogenase.[31] All hydrogenases catalyze reversible H2 uptake, but while the [FeFe] and [NiFe] hydrogenases are true redox catalysts, driving H2 oxidation and H+ reduction
    H2 ⇌ 2 H+ + 2 e−

I

K

  • Keyhole limpet hemocyanin
  • Each domain of a KLH subunit contains two copper atoms that together bind a single oxygen molecule (O2). When oxygen is bound to hemocyanin, the molecule takes on a distinctive transparent, opalescent blue color, due to the Cu2+ state of the copper. In the absence of oxygen, the bound copper is found as Cu1+ and hemocyanin is colorless.

M



  • Methane monooxygenase
  •  The active site in sMMO contains a di-iron center bridged by an oxygen atom (Fe-O-Fe), whereas the active site in pMMO utilizes copper, although some propose that pMMO also uses iron.

N

  • Nickel superoxide dismutase
  •  Nickel superoxide dismutase is primarily found in bacteria. The only know example of a eukaryote expressing a nickel containing superoxide dismutase is in the cytoplasm of a number of green algae species.[8] Ni-SOD was first isolated from Streptomyces bacteria, which are mostly found in soil. Streptomyces Ni-SOD has been the most heavily studied nickel containing SOD to date. These enzymes are now known to exist in a number of other prokaryotes, including cyanobacteria and several Actinomycetes species.
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  • Nitrile hydratase
  •  Metal cofactor In biochemistry, cobalt is in general found in a corrin ring, such as in vitamin B12. Nitrile hydratase is one of the rare enzyme types that use cobalt in a non-corrinoid manner. The mechanism by which the cobalt is transported to NHase without causing toxicity is unclear, although a cobalt permease has been identified, which transports cobalt across the cell membrane. The identity of the metal in the active site of a nitrile hydratase can be predicted by analysis of the sequence data of the alpha subunit in the region where the metal is bound. The presence of the amino acid sequence VCTLC indicates a Co-centred NHase and the presence of VCSLC indicates Fe-centred NHase.

O 

P

Type I photosystems use ferredoxin-like iron-sulfur cluster proteins as terminal electron acceptors, while type II photosystems ultimately shuttle electrons to a quinone terminal electron acceptor. Both reaction center types are present in chloroplasts and cyanobacteria, and work together to form a unique photosynthetic chain able to extract electrons from water, creating oxygen as a byproduct.
Structure
A reaction center comprises several (>10 or >11) protein subunits, that provide a scaffold for a series of cofactors. The cofactors can be pigments (like chlorophyll, pheophytin, carotenoids), quinones, or iron-sulfur clusters.[1]


R

  •  Since discovery of ribozymes by Thomas Cech and Sidney Altman in the early 1980s, ribozymes has been shown to be a distinct class of metalloenzymes.[32] Many ribozymes require metal ions in their active sites for chemical catalysis; hence they are called metalloenzymes. Additionally, metal ions are essential for the stabilization of ribozyme structure. Group I intron is the most studied ribozyme which has three metals participating in catalysis.[33] Other known ribozymes include group II intron, RNase P, and several small viral ribozymes (such as hammerhead, hairpin, HDV, and VS). Recently, four new classes of ribozymes have been discovered (named twister, twister sister, pistol and hatchet) which are all self-cleaving ribozymes.[34]
  • Rubredoxin
  •  Rubredoxins are a class of low-molecular-weight iron-containing proteins found in sulfur-metabolizing bacteria (pseudomonas) and archaea. Sometimes rubredoxins are classified as iron-sulfur proteins; however, in contrast to iron-sulfur proteins, rubredoxins do not contain inorganic sulfide.
  •  
  • Rubrerythrin
  •  Rubrerythrin is a non-haem iron protein involved in oxidative stress tolerance in anaerobic bacteria.[1] It contains a diiron site active site where peroxide is reduced to two water molecules and a mono-iron rubredoxin like domain thought to be involved in electron transfer.[2

S

  • Small copper carrier
  • Small copper carrier or SCC is a small molecule that transports copper in urine. It is excreted in the kidneys in humans or mice where the liver is unable to excrete excess copper in bile. This happens in Wilson’s disease where the presence of copper in urine is a diagnostic.[1] It was discovered by Lawrence Wilson Gray and Svetlana Lutsenko.[2] The molecule is 2 kDa. Its exact nature is not yet known but is presumed to be a peptide.[
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  • SOD1
  • Superoxide dismutase [Cu-Zn] also known as superoxide dismutase 1 or SOD1 is an enzyme that in humans is encoded by the SOD1 gene, located on chromosome 21. 
  • SOD2
  • Superoxide dismutase 2, mitochondrial (SOD2), also known as manganese-dependent superoxide dismutase (MnSOD), is an enzyme which in humans is encoded by the SOD2 gene on chromosome 6
  • Spore photoproduct lyase
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  • Sulfite oxidase
  •  The C-terminal domain hosts a molybdopterin cofactor that is surrounded by thirteen beta sheets and three alpha helices. The molybdopterin cofactor has a Mo(VI) center, which is bonded to a sulfur from cysteine, an ene-dithiolate from pyranopterin, and two terminal oxygens. It is at this molybdenum center that the catalytic oxidation of sulfite takes place.
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  • Superoxide dismutase
  •  Copper and zinc – most commonly used by eukaryotes, including humans. The cytosols of virtually all eukaryotic cells contain an SOD enzyme with copper and zinc (Cu-Zn-SOD).There are three major families of superoxide dismutase, depending on the protein fold and the metal cofactor: the Cu/Zn type (which binds both copper and zinc), Fe and Mn types (which bind either iron or manganese), and the Ni type (which binds nickel).

 T   

  • Troponin. In both cardiac and skeletal muscles, muscular force production is controlled primarily by changes in the intracellular calcium concentration. In general, when calcium rises, the muscles contract and, when calcium falls, the muscles relax. Troponin, along with actin and tropomyosin, is the protein complex to which calcium binds to trigger the production of muscular force.
  • Many transcription factors contain a structure known as a zinc finger, this is a structural module where a region of protein folds around a zinc ion. The zinc does not directly contact the DNA that these proteins bind to. Instead, the cofactor is essential for the stability of the tightly-folded protein chain.[43] In these proteins, the zinc ion is usually coordinated by pairs of cysteine and histidine side-chains.

 V

  • Vanabins
  • Vanabins (also known as vanadium-associated proteins or vanadium chromagen) are a specific group of vanadium-binding metalloproteins. Vanabins are found almost exclusively in the blood cells, or vanadocytes of some ascidians and tunicates (sea squirts). The vanabins extracted from tunicate vanadocytes are often called hemovanadins. These organisms are able to concentrate vanadium to a level more than 100 times higher than in the surrounding seawater. Vanabin proteins seem to be involved in collecting and accumulating this metal ion. At present there is no conclusive understanding of why these organisms collect vanadium, and it remains a biological mystery.
    German chemist Martin Henze discovered vanadium in ascidiaceans in 1911.

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