UNIPROT:Q07644 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UNIPROT:Q07644 (polypeptide)
72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Like other polypeptide hormones, purified intact parathyroid hormone (1-84)parathyroid hormone is notoriously unstable and is subject to large adsorptive losses in routine laboratory manipulation. The present studies were undertaken with 125I-labeled hormone to quantitate the problem and to develop preventative measures, particularly with concentrations of physiological interest, 1 . 10(-10) M. It was found that spontaneous cleavage of the hormone takes place upon its incubation in air or oxygen. This can be prevented by the presence of mercaptoethanol or by plasma levels of cysteine and ascorbate. Under non-cleavage conditions, adsorption was found to be extensive on all materials tested. This adsorption increased with time up to 2 h, was independent of ionic strength, increased with increasing temperature and was presumed to involve hydrophobic interactions. Under given conditions, adsorption was proportional to concentration (constant percentage). However, at very high concentrations, 1 . 10(-6) M, adsorption was markedly reduced. Adsorption was minimized at low pH (2). Bovine serum albumin reduced adsorption under all conditions when present at concentrations of 2 mg/ml or more. Coating laboratory ware with cetyl alcohol also was helpful. Using optimal conditions, cleavage is prevented and losses are less than 5% at neutral pH, and under 2% at pH 2.
...
PMID:The cleavage and adsorption of parathyroid hormone at high dilution: implications for receptor binding studies. 2 31

The formation of 3-hydroxyproline was studied with crude rat kidney cortex extract as a source of enzyme and chick embryo tendon protocollagen and procollagen or cartilage protocollagen as a substrate. Synthesis of 3-hydroxyproline was observed with all these substrates and the formation of 3-hydroxyproline ranged up to seven residues per pro-alpha-chain. The highest rate of 3-hydroxylation took place at 20 degrees C and the reaction required Fe2+, O2,2-oxoglutarate and ascorbate. The formation of 3-hydroxyproline was affected by chain length and the conformation of the substrate, in that longer polypeptide chains proved better substrates, while the native triple-helical conformation of protocollagen or procollagen completely prevented the reaction. Formation of 3-hydroxyproline with tendon procollagen as a substrate was not inhibited by antiserum to prolyl 4-hydroxylase or by poly(L-proline) when these substances were used in concentrations which clearly inhibited 4-hydroxyproline formation with tendon protocollagen as a substrate. Furthermore, pure prolyl 4-hydroxylase did not synthesize any 3-hydroxyproline under conditions in which the crude rat kidney cortex enzyme would readily do so. The data thus strongly suggest that prolyl 3-hydroxylase and prolyl 4-hydroxylase are separate enzymes.
...
PMID:Prolyl 3-hydroxylase: partial characterization of the enzyme from rat kidney cortex. 19 Dec 55

The coupled oxidation of leghaemoglobins with O(2) and ascorbate yielded oxyleghaemoglobin in the first reaction step, and the second step was the degradation of haem characterized by an A(675) increase. Leghaemoglobins were degraded to biliverdin isomers specifically, depending on the structure of the protein. The main leghaemoglobin components of Glycine (soya bean) and Phaseolus (kidney bean) were degraded to biliverdin mixtures containing about 50% of the beta-form, about 30% of the alpha-form and about 20% of the delta-isomer, whereas the leghaemoglobin I components of Vicia (broad bean) and Pisum (pea) were degraded almost exclusively to the beta-isomer, with traces of the alpha-isomer. The amino acid sequences of Glycine and Phaseolus leghaemoglobins resemble each other, as do those of Vicia and Pisum. The site specificity of bile-pigment formation from leghaemoglobins can be tentatively explained by specific differences in the amino acid sequences at those regions of the polypeptide chain that are in the vicinity of the appropriate methine bridges. The ligand-binding site in different leghaemoglobins may be outlined on the basis of the present results, supposing that the haem is degraded when a reduction product of haem-bound O(2) reacts with a methine bridge of the haem, and that the bridge specificity is regulated by hindering amino acid residues that determine the location of the bound O(2). The residue phenylalanine-CD1 appears to be further away from the haem plane or in a markedly more flexible position in leghaemoglobins than in mammalian globins. The haem-bound oxygen atom B, in Fe-O(A)-O(B), seems to be free to rotate in all directions except that of the gamma-bridge in Glycine and Phaseolus leghaemoglobins, but its position in Vicia and Pisum leghaemoglobin I might be restricted to the direction of the beta-methine bridge.
...
PMID:Bile-pigment formation from different leghaemoglobins. Methine-bridge specificity of coupled oxidation. 74 44

1. A reaction center from chloroplasts was purified by means of detergent treatment, differential centrifugation, column chromatography, and sucrose gradient. 2. The reaction center is active in NADP photoreduction by ascorbate. Ferredoxin, ferredoxin-NADP-reductase, and plastocyanin were required for the reaction. 3. The preparation contains five classes of polypeptide chains with apparent molecular weights of 70,000, 25,000, 20,000, 18,000 and 16,000 as determined by gel electrophoresis in sodium dodecyl sulfate. 4. Treatment with 0.5% sodium dodecyl sulfate abolished the NADP photoreduction activity and released the low molecular weight subunits, which were removed by sucrose gradient centrifugation from the high molecular weight ones. The P700 signal is associated with the 70,000 molecular weight polypeptide. 5. Antibody, prepared against the active reaction center, inhibited NADP photoreduction catalyzed by the purified reaction center as well as by isolated chloroplasts. The antibody interacted on immunodiffusion plates with any subchloroplast preparation capable of NADP photoreduction. It also interacted with the purified 70,000 molecular weight polypeptide. 6. It is concluded that both the primary oxidation and the primary reduction in Photosystem I are associated with the 70,000 molecular weight polypeptide.
...
PMID:Purification and properties of the photosystem I reaction center from chloroplasts. 80 81

The genomic clone named Bp10 contains a member of a small pollen-specific gene family of B. napus. The expression of the Bp10 gene family is maximal in early binucleate microspores and declines considerably in mature trinucleate pollen. Homologues of the Bp10 genes are expressed in the pollen of other plant species. The pollen-specific expression of the gene contained in the genomic clone was confirmed in tobacco plants transformed with a chimeric Bp10 promoter/GUS construct. A promoter fragment of 396 bp is sufficient to direct a strong and correct spatial and temporal expression in transgenic plants. The Bp10 gene family codes for proteins of 62 kDa showing approximately 30% sequence identify to cucumber and pumpkin ascorbate oxidases (AAOs). However, the AAO active centres are not conserved in the Bp10 products, suggesting an evolutionary relationship but a different enzymatic activity for these proteins. Expression of a recombinant Bp10 protein in E. coli inhibits bacterial growth on minimal medium, suggesting the production of an enzymatically active polypeptide in bacteria. No AAO activity could be correlated with the expression of the recombinant protein. Moreover, substances affecting AAO activity do not appear to influence the inhibitory activity of the protein produced in bacteria. However, as indicated by the rescue of bacterial growth in the presence of sodium bicarbonate or gaseous CO2, the Bp10 protein activity could be modulated by CO2 levels.
...
PMID:A Brassica napus gene family which shows sequence similarity to ascorbate oxidase is expressed in developing pollen. Molecular characterization and analysis of promoter activity in transgenic tobacco plants. 130 99

Short-term incubation of bovine alpha-crystallin with ascorbate alters the protein conformational stability. The denaturation curves with urea and guanidinium-chloride show different patterns, suggesting a deviation from a two-state mechanism owing to the presence of one or more intermediates in the unfolding of ascorbate-modified alpha-crystallin. Furthermore, the latter protein profiles are shifted to lower denaturant concentrations indicating a destabilizing action of ascorbate, which is capable of facilitating protein dissociation into subunits as demonstrated by gel filtration with 1.5 M-urea. The decrease in conformational stability cannot be ascribed to any major structural alteration, but rather to localized changes in the protein molecule. In fact, no difference between native and ascorbate-treated alpha-crystallin can be detected by amino acid analysis but perturbation of the tryptophan and tyrosine environment is indicated by alterations in intrinsic fluorescence. Furthermore, turbidity and light-scattering measurements suggest an involvement of the lysine side chains, since aggregability patterns with acetylsalicylic acid are significantly altered. The ascorbate-destabilizing effect on the conformational stability of alpha-crystallin, probably exerted through oxidative modification of amino acid residues and/or the formation of covalent adducts, provokes unfavourable steric interactions between residues along the polypeptide chains, thus favouring aggregation and insolubilization of crystallins which can lead to cataract formation, as also demonstrated by proteolytic digestion patterns which show a lower rate of degradation of the ascorbate-modified alpha-crystallin.
...
PMID:Conformational stability of bovine alpha-crystallin. Evidence for a destabilizing effect of ascorbate. 141 62

Excessive accumulation of collagen in the extracellular matrix has a crucial role in fibrosis. Thus pharmacological inhibition of collagen deposition is likely to be beneficial for patients suffering from fibrotic disorders such as liver cirrhosis. Prolyl 4-hydroxylase catalyzes the formation of 4-hydroxyproline in collagens and other proteins with collagen-like amino acid sequences by the hydroxylation of proline residues in -X-Pro-Gly- sequences. The reaction products, 4-hydroxyproline residues, serve to stabilize the collagen triple helices under physiological conditions. Conversely, collagen chains that contain no 4-hydroxyproline cannot fold into triple helical molecules that are stable at body temperature. The prolyl 4-hydroxylase reaction therefore seems to be a particularly suitable target for the pharmological regulation of excessive collagen formation. The reaction catalyzed by prolyl 4-hydroxylase requires Fe2+, 2-oxoglutarate, O2 and ascorbate and involves an oxidative decarboxylation of 2-oxoglutarate. The active enzyme is an alpha 2 beta 2 tetramer that consists of two types of inactive monomer and has two catalytic sites. Some parts of the catalytic sites may be built up cooperatively of both the alpha and beta subunits, but the alpha subunit appears to contribute the major part. The beta subunit contains the carboxyl-terminal tetrapeptide sequence -Lys-Asp-Glu-Leu which is essential for the retention of a polypeptide within the lumen of the endoplasmic reticulum. Since the alpha subunit lacks the carboxyl-terminal retention signal, one function of the beta subunit in the prolyl 4-hydroxylase tetramer may be to retain the enzyme within the endoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Prolyl 4-hydroxylase and its role in collagen synthesis. 166 65

Rat myocardial membranes exposed to the free radical-generating systems, Fe2+/ascorbate, Cu2+/t-butylhydro-peroxide, linoleic acid hydroperoxide, and soybean lipoxygenase (Type I) undergo lipid peroxidation. This is evidenced by the accumulation of thiobarbituric acid-reactive substances and the loss of both extractable phospholipids and their polyunsaturated acyl groups. Lipid peroxidation is accompanied by alterations of membrane proteins including the general loss of polypeptides and accumulation of high-molecular weight material. The most sensitive protein is a polypeptide with a molecular weight of 28 kDa. At low levels of oxidation, this protein moves incrementally to slightly higher apparent molecular weight. At higher oxidant levels or longer periods of oxidation, the protein disappears completely from the SDS-PAGE gel. The "28K reaction" occurs prior to the massive, oxidant-induced lipid alterations and may thus indicate specific adduct formation between this protein and certain peroxidized membrane phospholipids.
...
PMID:Free radical-induced alterations of myocardial membrane proteins. 191 Mar 12

Site-specific cleavage of proteins with metal chelates is an approach for designing artificial proteolytic reagents that are directed by proximity to a peptide bond rather than by an amino acid residue type. In the presence of ascorbate and H2O2, an iron chelate attached to Cys-212 of the enzyme human carbonic anhydrase I quickly cleaved the protein between residues Leu-189 and Asp-190 to produce two discrete fragments. The transfer of an 18O atom from [18O]H2O2 (or [18O]O2) to the carboxyl group of Leu-189 was demonstrated by mass spectrometry. Quantitative experiments revealed that one molecule of H2O2 and one molecule of ascorbate afforded the hydrolysis of one peptide bond (1:1:1 stoichiometry) and that the reaction required ascorbate and H2O2. The process is catalytic, since related experiments on the protein bovine serum albumin revealed two cleavage events for each polypeptide chain cleaved. Hydroxyl radical scavengers had no significant effect. These results may be explained by generation of a highly nucleophilic oxygen species, such as peroxide coordinated to the iron chelate, that attacks a carbonyl carbon nearby.
...
PMID:Transfer of oxygen from an artificial protease to peptide carbon during proteolysis. 196 24

Prolyl 4-hydroxylase (EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens by the hydroxylation of proline residues in X-Pro-Gly sequences. The reaction requires Fe2+, 2-oxoglutarate, O2, and ascorbate and involves an oxidative decarboxylation of 2-oxoglutarate. Ascorbate is not consumed during most catalytic cycles, but the enzyme also catalyzes decarboxylation of 2-oxoglutarate without subsequent hydroxylation, and ascorbate is required as a specific alternative oxygen acceptor in such uncoupled reaction cycles. A number of compounds inhibit prolyl 4-hydroxylase competitively with respect to some of its cosubstrates or the peptide substrate, and recently many suicide inactivators have also been described. Such inhibitors and inactivators are of considerable interest, because the prolyl 4-hydroxylase reaction would seem a particularly suitable target for chemical regulation of the excessive collagen formation found in patients with various fibrotic diseases. The active prolyl 4-hydroxylase is an alpha 2 beta 2 tetramer, consisting of two different types of inactive monomer and probably containing two catalytic sites per tetramer. The large catalytic site may be cooperatively built up of both the alpha and beta subunits, but the alpha subunit appears to contribute the major part. The beta subunit has been found to be identical to the enzyme protein disulfide isomerase and a major cellular thyroid hormone-binding protein and shows partial homology with a phosphoinositide-specific phospholipase C, thioredoxins, and the estrogen-binding domain of the estrogen receptor. The COOH-terminus of this beta subunit has the amino acid sequence Lys-Asp-Glu-Leu, which was recently suggested to be necessary for the retention of a polypeptide within the lumen of the endoplasmic reticulum. The alpha subunit does not have this COOH-terminal sequence, and thus one function of the beta subunit in the prolyl 4-hydroxylase tetramer appears to be to retain the enzyme within this cell organelle.
...
PMID:Protein hydroxylation: prolyl 4-hydroxylase, an enzyme with four cosubstrates and a multifunctional subunit. 253 73

1 2 3 4 5 6 7 8 9 Next >>