Search results for "Copper protein"

Are glutamate and asparagine necessary for tyrosinase activity of type-3 copper proteins?

2018

Abstract Type-3 copper proteins (T3CPs) are complex proteins which share similar active sites. Two copper atoms (CuA and CuB) bind dioxygen as a peroxide in a side on coordination. This protein family comprises the enzymes tyrosinase and catechol oxidase as well as the oxygen transporter hemocyanin. T3CPs occur in almost all organisms and exhibit a number of essential functions. In particular, they are involved in all kinds of enzymatic browning reactions and immune defense. The chemical basis of the two catalytic processes, i.e., the o-hydroxylation of monophenols and the two-electron oxidation to o-quinones, is still discussed. Investigations on natural enzymes with known crystal structur…

Paramagnetic NMR investigations of Co(II) and Ni(II) amicyanin.

1999

The paramagnetic 1H NMR spectra of the Co(II) and Ni(II) substituted forms of the type 1 blue copper protein (cupredoxin) amicyanin have been assigned. This is the first such analysis of a cupredoxin, which has a distorted tetrahedral active site with the ligands provided by two histidines, a cysteine and a methionine. The isotropic shifts of the resonances in these spectra are compared with those of Co(II) and Ni(II) azurin. A number of interesting similarities and differences are found. The coordination of the metal by the two equatorial histidine ligands is very similar in both proteins. The interaction between the introduced metal and the thiolate sulfur of the equatorial cysteine ligan…

NMR and homology modeling studies of copper(II)-halocyanin from Natronobacterium pharaonis bacteria

2004

Abstract Halocyanin from the haloalkaliphilic archaean Natronobacterium pharaonis is a peripheral membrane type 1 blue copper protein with a single polypeptide chain of 163 amino acid residues. Halocyanin participates as putative electron carrier protein associated to an electron acceptor role for a terminal oxidase and has the lowest redox potential value reported to date for a BCP. NMR studies and homology modeling calculations were performed to evaluate the electronic properties of Cu(II)-halocyanin from Natronobacterium pharaonis . The copper coordination site properties of Cu(II)-halocyanin are discussed. The 1 H NMR spectra, isotropic chemical shifts and relaxation times for halocyani…

1H-NMR study of a cobalt-substituted blue copper protein: Pseudomonas aeruginosa Co(II)-azurin.

1995

Substitution of copper by cobalt in blue copper proteins gives a paramagnetic metalloderivative suitable for paramagnetic NMR studies. A thorough analysis of the 1H-NMR spectrum of Pseudomonas aeruginosa Co(II)-azurin is presented here. All the observable contact-shifted signals as well as many other paramagnetic signals from protons placed up to about 1.0 nm around the metal center, including some residues belonging to functionally important parts of the protein like the hydrophobic patch and the His35 region, have been assigned. The results obtained permit the detection and study of structural variations like those originated by the His35 ionization, and allow us to draw a feasible pictur…

Hemocyanin conformational changes associated with SDS-induced phenol oxidase activation.

2007

The enzymatic activity of phenoloxidase is assayed routinely in the presence of SDS. Similar assay conditions elicit phenoloxidase activity in another type 3 copper protein, namely hemocyanin, which normally functions as an oxygen carrier. The nature of the conformational changes induced in type 3 copper proteins by the denaturant SDS is unknown. This comparative study demonstrates that arthropod hemocyanins can be converted from being an oxygen carrier to a form which exhibits phenoloxidase activity by incubation with SDS, with accompanying changes in secondary and tertiary structure. Structural characterisation, using various biophysical methods, suggests that the micellar form of SDS is …

Functional Changes in the Family of Type 3 Copper Proteins During Evolution

2004

The integrative and evolutionary biology of gas-binding copper proteins: an introduction.

2011

This article summarizes the contributions given at the symposium "The Benefits of Gas-binding Proteins. Integrative and Evolutionary Physiology of Copper Proteins: Molecules to Organisms and their Environment," presented at the First International Congress of Respiratory Biology, August 14-16, at Bad Honnef/Bonn, Germany.

Electronic characterisation of the oxidized state of the blue copper protein Rusticyanin by 1 H NMR: Is the axial methionine the dominant influence f…

2001

The oxidized state of rusticyanin, the blue copper protein with the highest redox potential in its class, has been investigated through (1)H nuclear magnetic resonance applied to its cobalt(II) derivative. The assignment of the protons belonging to the coordinated residues has been performed. Many other amino acids situated in the vicinity of the metal ion, including six hydrophobic residues (isoleucine140 and five phenylalanines) have also been identified. The orientation of the main axes of the magnetic susceptibility tensor for the cobalt(II)-rusticyanin as well as its axial, Deltachi(ax), and rhombic, Deltachi(rh), magnetic susceptibility anisotropy components have been determined. A co…

Cupredoxin-like domains in haemocyanins

2010

Haemocyanins are multimeric oxygen transport proteins, which bind oxygen to type 3 copper sites. Arthropod haemocyanins contain 75-kDa subunits, whereas molluscan haemocyanins contain 350–400-kDa subunits comprising seven or eight different 50 kDa FUs (functional units) designated FU-a to FU-h, each with an active site. FU-h possesses a tail of 100 amino acids not present in the other FUs. In the present study we show by X-ray crystallography that in FU-h of KLH1 (keyhole-limpet-haemocyanin isoform 1) the structure of the tail domain is cupredoxin-like but contains no copper. The copper-free domain 3 in arthropod haemocyanin subunits has also recently been reinterpreted as being cupredoxin-…

Similar enzyme activation and catalysis in hemocyanins and tyrosinases

2006

This review presents the common features and differences of the type 3 copper proteins with respect to their structure and function. In spite of these differences a common mechanism of activation and catalysis seems to have been preserved throughout evolution. In all cases the inactive proenzymes such as tyrosinase and catecholoxidase are activated by removal of an amino acid blocking the entrance channel to the active site. No other modification at the active site seems to be necessary to enable catalytic activity. Hemocyanins, the oxygen carriers in many invertebrates, also behave as silent inactive enzymes and can be activated in the same way. The molecular basis of the catalytic process…