Proteins secondary transformations

The conformational changes which have been described so far are probably all relatively small local changes in the structure of H,K-ATPase. This has been confirmed by Mitchell et al. [101] who demonstrated by Fourier transform infrared spectroscopy that a gross change in the protein secondary structure does not occur upon a conformational change from Ei to 3. Circular dichroism measurements, however [102,103], indicated an increase in a-helical structure upon addition of ATP to H,K-ATPase in the presence of Mg and... 

A review by Dong et al. [3.57] provides an overview of how Fourier transform JR spectroscopy can be used to study protein stabilization and to prevent lyophilization- induced protein aggregation. An introduction to the study of protein secondary structures and the processing and interpretation of protein IR spectra is given. 

Some special features of proteins are elaborated by secondary transformations that are not part of the translation process. The A-formylmethionine initiator may be hydrolysed to methionine, or, as we have already indicated, the methionine unit may be removed altogether. Other post-translational changes to individual amino acids may be seen, e.g. the hydroxylation of proline to hydroxyproline (see Section 13.1) or the generation of disulfide bridges between cysteine residues (see Section 13.3). 

Surewicz, W.K., Mantsch, H.H., Chapman, D. (1993). Determination of protein secondary structure by Fourier transform infrared spectroscopy A critical assessment. Biochemistry, 32, 389-394. 

Prestrelski SJ, Byler DM, Liebman MN. Generation of a substructure library for the description and classification of protein secondary structure. II. Application to spectrastructure correlations in Fourier transform infrared spectroscopy. Proteins 1992 14 440-450. 

Fourier transform infrared microspectroscopy detects changes in protein secondary structure associated with desiccahon tolerance in developing maize embryos. Plant Physiol, 116, 1169-77. 

He WZ, Newell WR, Haris PI et al. Protein secondary struaure of the isolated photosystem II reaction center and conformational changes studies by Fourier transform infrared spectroscopy. Biochemistry 1991 30 4552-4559. 

The spectra and the relative ratio of the secondary conformations (a-helix and (3-sheet) of prion infected brains in frozen sectioned tissue were measured by Fourier-transform infrared (FT-IR) microscopy. The tissues were obtained from the Prion Diseases Research Center in the National Animal Health Institute (PDRC/NAHI) of Japan. Both prion infected and normal brain tissues of mice and hamster were embedded adjacently and were frozen-sectioned for the FT-IR microscopy. Spectra from the normal and the prion-infected brain tissue sides were compared. The C-H stretching components in the normal tissue and the amide-I, -II components in the prion tissue were larger than the other sides, respectively. Furthermore, we developed the software to analyze the relative ratios of protein secondary conformation in the tissue by FT-IR microscopy. Results showed that the relative ratio of the p-sheet component was at a higher level (37-40%) in the prion side compared to that in the normal... 

Their simple model assumes that each denatured protein molecule transforms irreversibly in a first order reaction into a species from which the native form cannot be recovered. This model is called Lumry-Eyring model [55] since Lumry and Eyring were among the first to propose that proteins unfold in two steps, a reversible unfolding equilibrium of the tertiary structure followed by a first order, irreversible step involving secondary structure unfolding. 

Prions—protein particles that lack nucleic acid— cause fatal transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease, scrapie, and bovine spongiform encephalopathy. Prion diseases involve an altered secondary-tertiary strucmre of a namrally occurring protein, PrPc. When PrPc interacts with its pathologic isoform PrPSc, its conformation is transformed from a predominantly a-helical strucmre to the P-sheet strucmre characteristic of PrPSc. 

Lipid hydroperoxides are either formed in an autocatalytic process initiated by hydroxyl radicals or they are formed photochemically. Lipid hydroperoxides, known as the primary lipid oxidation products, are tasteless and odourless, but may be cleaved into the so-called secondary lipid oxidation products by heat or by metal ion catalysis. This transformation of hydroperoxides to secondary lipid oxidation products can thus be seen during chill storage of pork (Nielsen et al, 1997). The secondary lipid oxidation products, like hexanal from linoleic acid, are volatile and provide precooked meats, dried milk products and used frying oil with characteristic off-flavours (Shahidi and Pegg, 1994). They may further react with proteins forming fluorescent protein derivatives derived from initially formed Schiff bases (Tappel, 1956). 

The availability of the purified transporter in large quantity has enabled investigation of its secondary structure by biophysical techniques. Comparison of the circular dichroism (CD) spectrum of the transporter in lipid vesicles with the CD spectra of water-soluble proteins of known structure indicated the presence of approximately 82% a-helix, 10% ) -turns and 8% other random coil structure [97]. No / -sheet structure was detected either in this study or in a study of the protein by the same group using polarized Fourier transform infrared (FTIR) spectroscopy [98]. In our laboratory FTIR spectroscopy of the transporter has similarly revealed that... 

A central element in the prediction of secondary structure is the periodicity of sequence conservation, which has proven to be a good indicator in a number of membrane proteins (5). The periodicity is quantified by Fourier transform (FT) analysis. A... 

The herbicide alachlor (4.146, Fig. 4.7) also displayed species-dependent toxicity, since it induced nasal tumors in rats but not in mice. Its metabolic scheme in rats and mice (Fig. 4.7) shows that alachlor can be transformed into 2,6-diethylaniline (4.149) by two different pathways, one of which proceeds via formation of 4.147. The other pathway implies glutathione (GSH) conjugation, followed by /3-lyase-mediated liberation of the thiol, followed by S-methylation to produce the methylsulfide 4.148. The two secondary amides 4.147 and 4.148 were hydrolyzed by microsomal arylamidases, but alachlor itself was not a substrate for this enzyme. The hydrolytic product 2,6-diethylaniline (4.149) was oxidized in nasal tissues to the electrophilic quinonimine metabolite 4.150, which can bind covalently to proteins. Aryl-... 

Vandenbussche G, Clercx A, Clercx M, et al. Secondary structure and orientation of the surfactant protein SP-B in a lipid environment. A Fourier transform infrared spectroscopy study. Biochemistry 1992 31(38) 9169-9176. 

Fourier transform infrared/photoacoustic spectroscopy (FT-IR/PAS) can be used to evaluate the secondary structure of proteins, as demonstrated by experiments on concanavalin A, hemoglobin, lysozyme, and trypsin, four proteins having different distributions of secondary... 

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