Histidyl-histidine

Shen, C., Lazcano, A., and Or6, J. (1990a). The enhancement activities of histidyl-histidine in some prebiotic reactions. J. Mol. Evol, 31, 445-52. 

A review3 with 57 references discusses the interaction of Ptn and Pd11 with histidine and histidyl containing peptides. The coordinating behavior of histidyl containing peptides towards Pt11 and Pd11 depends on the histidyl position in the peptide sequence. 

H.S. Mandal and H.-B. Kraatz, Ferrocene-histidine conjugates N-ferrocenoyl-histidyl(imN-ferrocenoyl)methylester synthesis and structure. J. Organomet. Chem. 674, 32-37 (2003). 

FIGURE 6.10 The side chain of histidine is readily acylated (A) by activated residues. The imidazolide produced is an activated species similar to the intermediate generated by reaction (B) of a carboxylic acid with coupling reagent carbonyldiimidazole. (Staab, 1956). Imida-zolides acylate amino and hydroxyl groups. Isomerization of histidyl during activation results from abstraction (C) of the a-proton by the 7t-nitrogen. 

Among protein aromatic groups, histidyl residues are the most metal reactive, followed by tryptophan, tyrosine, and phenylalanine.1 Copper is the most reactive metal, followed in order by nickel, cobalt, and zinc. These interactions are typically strongest in the pH range of 7.5 to 8.5, coincident with the titration of histidine. Because histidine is essentially uncharged at alkaline pH, complex-ation makes affected proteins more electropositive. Because of the alkaline optima for these interactions, their effects are most often observed on anion exchangers, where complexed forms tend to be retained more weakly than native protein. The effect may be substantial or it may be small, but even small differences may erode resolution enough to limit the usefulness of an assay. 

This bacterial ADPRtransferase inactivates host cell ri-bosomal elongation factor eEF-2 by NAD+-dependent covalent modification of diphthamide, an acceptor-modified histidyl residue, 2-[3-carboxyamido-3-(trimethylam-monio)propyl]histidine. 

This enzyme [EC 6.1.1.21], also referred to as histi-dinedRNA ligase, catalyzes the reaction of histidine with tRNA and ATP to produce histidyl-tRNA , AMP, and pyrophosphate. See also Aminoacyl-tRNA Synthetases... 

Another zinc-utilizing enzyme is carbonate/dehydratase C (Kannan et al., 1972). Here, the zinc is firmly bound by three histidyl side chains and a water molecule or a hydroxyl ion (Fig. 27). The coordination is that of a distorted tetrahedron. Metals such as Cu(II), Co(Il), and Mn(ll) bind at the same site as zinc. Hg(II) also binds near, but not precisely at, this site (Kannan et al., 1972). Horse liver alcohol dehydrogenase (Schneider et al., 1983) contains two zinc sites, one catalytic and one noncatalytic. X-Ray studies showed that the catalytic Zn(II), bound tetrahedrally to two cysteines, one histidine, and water (or hydroxyl), can be replaced by Co(II) and that the tetrahedral geometry is maintained. This is also true with Ni(Il). Insulin also binds zinc (Adams etai, 1969 Bordas etal., 1983) and forms rhombohedral 2Zn insulin crystals. The coordination of the zinc consists of three symmetry-related histidines (from BIO) and three symmetry-related water molecules. These give an octahedral complex... 

Mitochondrial succinate dehydrogenase, which catalyzes the reaction of Eq. 15-21, contains a flavin prosthetic group that is covalently attached to a histidine side chain. This modified FAD was isolated and identified as 8a-(Ne2-histidyl)-FAD 219 The same prosthetic group has also been found in several other dehydrogenases.220 It was the first identified member of a series of modified FAD or riboflavin 5 -phosphate derivatives that are attached by covalent bonds to the active sites of more than 20 different enzymes.219... 

Many proteins have structures related to those of aminoacyl-tRNA synthetases.282 283 For example, asparagine synthetase A functions via an aspartyl-adenylate intermediate (Chapter 24, Section B), and its structure resembls that of aspartyl-tRNA synthetase.284 The his G gene of histidine biosynthesis (Fig. 25-13) encodes an ATP phosphoribosyltransferase with structural homology to the catalytic domain of histidyl-tRNA synthetase.284 The reason is not clear, but some aminoacyl-tRNA synthetases, especially the histidyl-tRNA synthetase, are common autoantigens for the inflammatory disease polymyosititis.285 286... 

Proximal Histidyl NzH Resonances. In the H NMR spectrum of deoxy-Hb A in H2O two low-field resonances occur at + 58.5 and +71.6 ppm downfield from H20 (La Mar et al., 1977 Takahashi et al., 1980). These two resonances disappear in the presence of D20 and have been assigned to the hyperfine-shifted NsH-exchangeable protons of the proximal histidyl residues (F8) of the a and p chains of deoxy-Hb A (Takahashi et al., 1980 La Mar et al., 1980). In Fig. 17, it is clear that the resonance at + 71 ppm is missing in Hb M Milwaukee, suggesting that this resonance comes from the p chain and the resonance at +58.5 ppm from the a chain. Hb M Boston has only the resonance at +71 ppm, which confirms the assignment of the +71-ppm resonance to the N8H proton of the proximal histidine of the P chain and the + 58.5-ppm resonance to the corresponding residue in the a chain (Takahashi et al., 1980). The fact that the a- and P-heme resonances are clearly separated indicates that the conformations of the proximal histidyl residues are different in the a and P chains of deoxy-Hb A. 

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