Glutamate residues

FIGURE 6.1 All electrostatic interaction between the e-amino group of a lysine and the 7-carboxyl group of a glutamate residue. 

It has a molecular weight of about 34000 and contains one Zn tetrahedrally coordinated to two histidine N atoms, a carboxyl O of a glutamate residue, and a water molecule. The precise mechanism of its action is not finally settled in spite of the intensive study of model systems, but it is agreed that the first step is coordination of... 

The isomerization of isopentenyl diphosphate to dimethylally diphos phate is catalyzed by JPP isomerase and occurs through a carbocation pathway Protonation of the IPP double bond by a hydrogen-bonded cysteine residue ir the enzyme gives a tertiary carbocation intermediate, which is deprotonated b a glutamate residue as base to yield DMAPP. X-ray structural studies on the enzyme show that it holds the substrate in an unusually deep, well-protectec pocket to shield the highly reactive carbocation from reaction with solvent 01 other external substances. 

Vitamin K is the cofactor for the carboxylation of glutamate residues in the post-synthetic modification of proteins to form the unusual amino acid y-carboxygluta-mate (Gla), which chelates the calcium ion. Initially, vitamin K hydroquinone is oxidized to the epoxide (Figure 45-8), which activates a glutamate residue in the protein substrate to a carbanion, that reacts non-enzymically with carbon dioxide to form y-carboxyglut-amate. Vitamin K epoxide is reduced to the quinone by a warfarin-sensitive reductase, and the quinone is reduced to the active hydroquinone by either the same warfarin-sensitive reductase or a warfarin-insensitive... 

The active form of fohc acid (pteroyl glutamate) is tetrahydrofolate (Figure 45-15). The folates in foods may have up to seven additional glutamate residues linked by y-peptide bonds. In addition, all of the one-carbon substituted folates in Figure 45-15 may also be present in foods. 

Vitamin E (tocopherol) is the most important antioxidant in the body, acting in the lipid phase of membranes and protecting against the effects of free radicals. Vitamin K functions as cofactor to a carboxylase that acts on glutamate residues of clotting factor precursor proteins to enable them to chelate calcium. 

For activity, factors II, VII, IX, and X and proteins C and S require vitamin K-dependent y-carboxylation of certain glutamate residues, a process that is inhibited by the anticoagulant warfarin. 

Factor IX 415 amino acids glycosylated modified residues Mammalian cells Treatment of Christmas disease Approved for sale Must be made in mammalian cells since glycosylation and conversion of first 12 glutamate residues to pyroglutamate essential for activity... 

Leimkiihler S, AL Stockert, K Igarashi, T Nishino, R Hille (2004) The role of active site glutamate residues in catalysis of Rhodobacter capsulatus xanthine dehydrogenase. J Biol Chem 279 40437-40444. 

Fig. 2. Possible structures for a diiron(III) peroxide unit in the peroxo intermediate consistent with available Raman and Mossbauer spectroscopic data. The symbols N and 0 designate nitrogen and oxygen donor atoms of histidine and glutamate residues, respectively. Some of the latter must be bidentate to fill the coordination spheres.

The specificity determinants surrounding the tyrosine phospho-acceptor sites have been determined by various procedures. In PTK assays using various substrates, it was determined that glutamic residues of the N-terminal or C-terminal side of the acceptor are often preferred. The substrate specificity of PTK catalytic domains has been analyzed by peptide library screening for prediction of the optimal peptide substrates. Finally, bioinformatics has been applied to identify phospho-acceptor sites in proteins of PTKs by application of a neural network algorithm. 

Sickle cell disease is caused by a mutation that results in the substitution of a valine residue for a glutamate residue in the sixth position of the hemoglobin P-chain. This results from the substitution of a T for an A in the glutamate codon. When (1) DNA from a patient... 

Figure 2.11 y-Carboxylation of glutamate residues (Glu) yields y-carboxyglutamate (Gla), whereas (3-hydroxy lation of aspartate (Asp) yields (3-hydroxyaspartate (Hya) and (3-hydroxylation of asparagine (Asn) yields 3-hydroxyasparagine (Hyn)... 

Nixon You showed that the glutamate residue was preserved through all three subtypes. Yet when you express each of the different subtypes and look at the Ca2+ oscillations, they are different. The type 3 InsP3 receptor doesn t produce oscillations. Does that mean that this residue is not always involved in the same way It is preserved there in the type 3 and you don t see Ca2+ oscillation. 

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