Protein as acceptors

With an iron-sulphur protein as acceptor Acting on single donors with incorporation of molecular oxygen (oxygenases) 1.18 1.18.1 Acting on reduced ferredoxin as donor With NAD+ or NADP+ as acceptor... 

The tyrosine protein sulfotransferase preparations from Golgi-enriched membranes have been used for sulfation of synthetic mono- and multiple-tyrosine peptides related to known sulfation sites in proteins and peptides at analytical levels to establish the enzyme specificities.1f11-13] Preparative sulfations have not been carried out to date. A novel type of arylsulfotransferase produced by Eubacterium A-44 which is part of the human intestinal flora, has recently been discovered.1"1911111 This enzyme catalyzes the transfer of a sulfate group from phenolic sulfate, but not from 3 -phosphadenosine-5 -phosphasulfate, to other phenolic compounds. Using 4-nitrophenylsulfate as a donor substrate and tyrosine-containing peptides and proteins as acceptor substrates it catalyzes the specific sulfation of the tyrosine residues.11111-112 While this enzyme very efficiently sulfates tyrosine derivatives, the... 

The strong hydrogen bonds formed between the solvent and the protein solute, particularly between the solvent as donor and the amide C=0 groups of the protein as acceptor. This factor has already been discussed in connection with synthetic polypeptides. Section IV,D. 

Proteases are enzymes that break peptide bonds in proteins. As such they lend themselves to a variety of homogeneous assay techniques. Most employ labeling both ends of the substrate with a different tag, and looking for the appearance (disappearance) of the signal generated in the intact substrate (product). As an example, for a fluorescence quench assay, the N-terminal of a peptide is labeled with DNP and the C-terminal with MCA. As such, the peptide is fluorescently silent since the fluorescence from DNP is quenched by absorption by the MCA. Another very popular donor/acceptor pair is EDANS 5-[(2-aminoethyl)amino] naphthalene-1-sulfonic acid and DABCYL 4-(4-dimethylaminophenylazo)benzoic acid) (a sulfonyl derivative (DABSYL) [27], Upon peptide cleavage, the two products diffuse, and due to a lack of proximity, the fluorescence increases. 

Liao F, Xie Y, Yang X et al (2009) Homogeneous noncompetitive assay of protein via Forster-resonance-energy-transfer with tryptophan residue(s) as intrinsic donor(s) and fluorescent ligand as acceptor. Biosens Bioelectron 25 112-117... 

There are many different H-bond donors as well as acceptors in proteins and nucleic acids which contribute to the specific recognition. Important H-bond donors and acceptors in proteins are Asn, Gin, Ser, Thr, Tyr, Glu, Asp, Arg, Lys, Cys and His. The peptide bonds of the backbone often participate, as well. 

Propionibacteria can produce pyruvate either from glucose, primarily via the EMP pathway, or from oxidation of lactate by using a flavo-protein as a hydrogen acceptor (Gottschalk 1979). As shown in Figure... 

Macrophages and cytokines can also influence lipoprotein metabolism [139], Grove et al. indicated that macrophages can secrete several proteins, including 27-oxygenated metabolites of cholesterol, that upregulate LDL receptors in HepG2 cells [140], This mechanism was compared with the classical HDL-dependent reverse cholesterol transport. With albumin as extracellular acceptor, the major secreted product was 3-/3-hydroxy-5-cholestenoic acid with HDL as acceptor, 27-hydroxycholesterol was the major secreted product [140, 141]. 

The principal function of cyt. c is to form complexes through a defined interface with protein partners in our cells. This is most established for eukaryotic cytochrome c within the mitochondrial electron transport chain (ETC), a process required for carrying out the oxidative phosphorylation of ATP.4 Formation of a complex with cyt. c reductase (an electron-donor protein from complex III) and cyt. c oxidase (an electron-acceptor protein from complex IV) leads to the transfer of electrons between otherwise separated proteins. More recently cyt. c has been found to play a critical role in the process of apoptosis or programmed cell death This in turn has led to a resurgence of interest in all aspects of cyt. c research.5 Again protein-protein interactions have been shown be essential with mitochrondrial cyt. c binding to such proteins as APAF-1 to form the multi-protein species known as the apoptosome that is now thought to be a requirement for apoptosis.6,7... 

With the availability of labeled hormones of high specific activity and the application of the principles of affinity chromatography, researchers were able to isolate cellular proteins that bind to plant hormones in vitro. Such proteins have been referred to as receptor proteins, binding proteins, or acceptor proteins. Tacit in the concept of hormone receptor proteins is the stereo-specific interaction of the hormone and the receptor protein (19). The resulting hormone-protein complex participates in growth processes that depend on new or enhanced protein synthesis. Advances in molecular biology and related sciences have enabled many researchers to study the role of receptors in the control of nuclear functions or other activities and to determine the site of primary hormonal action. 

The synthetase consists of the three modules E1, E2, and E3 (for a complete description, see Sec. II. A). Each module is composed of an activation site forming the acyl or aminoacyl adenylate, a carrier domain which is posttranslationally modified with 4 -phosphopantetheine (Sp), and a condensation domain (Cl, C2) or, alternatively, a structurally similar epimerization domain (Ep). Activation of aminoadipate (Aad) leads to an acylated enzyme intermediate, in which Aad is attached to the terminal cysteamine of the cofactor (El-Spl-Aad) [reactions (1) and (2)]. Likewise, activation of cysteine (Cys) leads to cysteinylated module 2 [reactions (3) and (4)]. For the condensation reaction to occur between aminoadipate as donor and cysteine as acceptor, both intermediates are thought to react at the condensation site of module 1 (Cl). Each condensation site is composed, in analogy to ribosomal peptide formation, of an aminoacyl and a peptidyl site. In this case of initiation, the thioester of Aad enters the P-site, while the thioester of Cys enters the A-site. Condensation occurs and leaves the dipeptidyl intermediate Aad-Cys at the carrier protein of the second module [reaction (5)]. The third amino acid valine is activated on module 3, and Val is attached to the carrier protein 3 [reactions (6) and (7)]. Formation of the tripeptide occurs at the second condensation site C2, with the dipeptidyl intermediate entering the P-site and the valiny 1-intermediate the A-site [reaction (8)]. 

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