scholarly journals Conformational changes in human lens proteins in cataract

1972 ◽  
Vol 129 (1) ◽  
pp. 97-100 ◽  
Author(s):  
John J. Harding
Keyword(s):  
Conformational Changes ◽  
Tryptic Digestion ◽  
Human Lens ◽  
Thiol Groups ◽  
Protein Thiol ◽  
Lens Proteins ◽  
Normal Human ◽  
Almost All

The reactivity of protein thiol groups in human lens and the susceptibility of the proteins to tryptic digestion were investigated. Both were found to be greater in some cataractous lenses, indicating that lens proteins have unfolded during cataractogenesis. Almost all the tyrosine in the proteins of the normal human lens reacts with tetranitromethane and is therefore probably on the outside of the major lens proteins.

scholarly journals The effect of tropomyosin on the adenosine triphosphatase activity of desensitized actomyosin

1967 ◽  
Vol 105 (3) ◽  
pp. 1235-1243 ◽  
Author(s):  
M. C. Schaub ◽  
S V Perry ◽  
D. J. Hartshorne
Keyword(s):  
Acetic Acid ◽  
Inhibitory Activity ◽  
Adenosine Triphosphatase ◽  
Inhibitory Effect ◽  
Tryptic Digestion ◽  
Prolonged Treatment ◽  
Thiol Groups ◽  
Protein Thiol ◽  
Adenosine Triphosphatase Activity ◽  
Inhibitory Activities

1. Tropomyosin preparations of the Bailey type, and those prepared in the presence of dithiothreitol to prevent oxidation of protein thiol groups, inhibit the Ca2+-activated adenosine triphosphatase (ATPase) of desensitized actomyosin by up to 60%. 2. The inhibitory activity of myofibrillar extracts and tropomyosin survives various agents known to denature proteins but to the action of which tropomyosin is unusually stable, namely heating at 100° and mild tryptic digestion. It is destroyed by prolonged treatment with trypsin. 3. The ethylenedioxybis-(ethyleneamino)tetra-acetic acid (EGTA)-sensitizing factor present in extracts of natural actomyosin and myofibrils could be selectively destroyed, leaving unchanged the inhibitory effect on the Ca2+-activated ATPase. There was no correlation between the EGTA-sensitizing and the Ca2+-activated inhibitory activities of tropomyosin prepared under different conditions. 4. Optimum inhibition was achieved when tropomyosin and the myosin of desensitized actomyosin were present in approximately equimolar proportions. Tropomyosin had no effect on the Ca2+-activated ATPase of myosin measured under similar conditions. 5. Evidence is presented showing that the tropomyosin binds to desensitized actomyosin under the conditions in which the ATPase is inhibited.

scholarly journals Structure Elucidation of a Novel Yellow Chromophore from Human Lens Protein

2004 ◽  
Vol 279 (44) ◽  
pp. 45441-45449 ◽  
Author(s):  
Rongzhu Cheng ◽  
Qi Feng ◽  
Ognyan K. Argirov ◽  
Beryl J. Ortwerth
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Water Soluble ◽  
Human Lens ◽  
Lens Protein ◽  
Two Dimensional ◽  
Cross Link ◽  
Lens Proteins ◽  
Lysine Residues ◽  
Normal Human

We report here the isolation of a novel acid-labile yellow chromophore from the enzymatic digest of human lens proteins and the identification of its chemical structure by liquid chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, and1H,13C, and two-dimensional NMR. This new chromophore exhibited a UV absorbance maximum at 343 nm and fluorescence at 410 nm when excited at 343 nm. Analysis of the purified compound by reversed-phase HPLC with in-line electrospray ionization mass spectrometry revealed a molecular mass of 370 Da. One- and two-dimensional NMR analyses elucidated the structure to be 1-(5-amino-5-carboxypentyl)-4-(5-amino-5-carboxypentylamino)-3-hydroxy-2,3-dihydropyridinium, a cross-link between the ϵ-amino groups of two lysine residues, and a five-carbon ring. Because this cross-link contains two lysine residues and a dihydropyridinium ring, we assigned it the trivial name of K2P. Quantitative determinations of K2P in individual normal human lens or cataract lens water-soluble and water-insoluble protein digests were made using a high-performance liquid chromatograph equipped with a diode array detector. These measurements revealed a significant enhancement of K2P in cataract lens proteins (613 ± 362 pmol/mg of water-insoluble sonicate supernatant (WISS) protein or 85 ± 51 pmol/mg of WS protein) when compared with aged normal human lens proteins (261 ± 93 pmol/mg of WISS protein or 23 ± 15 pmol/mg of water-soluble (WS) protein). These data provide chemical evidence for increased protein cross-linking during aging and cataract developmentin vivo. This new cross-link may serve as a quantitatively more significant biomarker for assessing the role of lens protein modifications during aging and in the pathogenesis of cataract.

scholarly journals Reaction of tyrosine oxidation products with proteins of the lens

1968 ◽  
Vol 109 (2) ◽  
pp. 301-305 ◽  
Author(s):  
Antoinette Pirie
Keyword(s):  
Ascorbic Acid ◽  
Fluorescence Spectra ◽  
Ferrous Sulphate ◽  
Oxidation Products ◽  
Thiol Groups ◽  
Lens Proteins ◽  
Bovine Lens ◽  
Tyrosine Oxidation ◽  
Cataractous Lens

Oxidation of tyrosine in the presence of bovine lens proteins leads to the formation of brown or black melanoproteins. Both tyrosinase and the oxidizing system of ferrous sulphate–ascorbic acid–EDTA are effective. The fluorescence of the lens proteins is both altered and enhanced by the tyrosine-oxidizing systems. Their fluorescence spectra resemble those of urea-insoluble proteins of human cataractous lens and of 1,2-naphthaquinone–proteins of naphthalene cataract. The lens proteins lose their thiol groups and, in acid hydrolysates of treated β-and γ-crystallins, a substance has been detected chromatographically that behaves similarly to a compound formed when 3,4-dihydroxyphenylalanine (dopa) is oxidized by tyrosinase in the presence of cysteine. Analysis and behaviour of this substance from hydrolysates of lens proteins suggest that it is a compound of cysteine and dopa.

Effect of Vernonia cognata on oxidative damage induced by ethanol in rats

2010 ◽  
Vol 30 (7) ◽  
pp. 675-684 ◽  
Author(s):  
CS Mota ◽  
RB Freitas ◽  
ML Athayde ◽  
AA Boligon ◽  
PR Augusti ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
High Performance ◽  
Tissue Injury ◽  
Antioxidant Effect ◽  
Gastric Tissue ◽  
Thiol Groups ◽  
Protein Thiol ◽  
Stress Markers ◽  
Hydroethanolic Extract ◽  
And Oxidative Stress

Free radicals production and oxidative stress play a central role in injuries caused by ethanol (EtOH) on gastric mucosal. Thus, strategies to counteract EtOH toxicity are highly desirable. This study was aimed at evaluating whether Vernonia cognata extract would reduce EtOH effects in rats. Rats received Vernonia cognata extract (0, 1 and 2 g/kg bw, by gavage) 1 hour after EtOH had been administered (0 or 70%, 0.5 mL/100 g bw, by gavage) and were killed 1 hour after Vernonia cognata extract administration. The stomach was removed for macroscopic and histopathological evaluation, as well as, oxidative stress markers such as lipoperoxidation (LPO) and non-protein thiol groups (NPSH) levels and catalase (CAT) activity. EtOH acute exposure increased LPO and decreased NPSH levels and CAT activity along with macroscopic and microscopic lesions in gastric tissue, confirming the involvement of oxidative stress in EtOH toxicity. Vernonia cognata extract attenuated oxidative and histopathological features induced by EtOH at all evaluated doses. Moreover, both studied doses of Vernonia cognata extract caused an increase in NPSH levels per se. However, only the dose of 2 g/kg reverted all macroscopic changes caused by EtOH toxicity. The protective effect of the extract could be attributed to antioxidant molecules present in the extract, such as flavonoids and phenolic acids, which were quantified by high performance liquid chromatography (HPLC). Thus, an antioxidant effect of the extract leads to a protection on gastric tissue. Our results indicate that Vernonia cognata hydroethanolic extract could have a beneficial role against EtOH toxicity by preventing oxidative stress and gastric tissue injury.

scholarly journals Dissociation, unfolding and refolding trials of pig kidney 3,4-dihydroxyphenylalanine (dopa) decarboxylase

1993 ◽  
Vol 295 (2) ◽  
pp. 493-500 ◽  
Author(s):  
P Dominici ◽  
P S Moore ◽  
C Borri Voltattorni
Keyword(s):  
Conformational Changes ◽  
Dopa Decarboxylase ◽  
Experimental Conditions ◽  
High Tendency ◽  
Denatured Protein ◽  
Pig Kidney ◽  
Plausible Model ◽  
Spectroscopic Characteristics ◽  
Equilibrium Transition ◽  
Almost All

The effect of guanidinium chloride (GuCl) on enzyme activity, hydrodynamic volume, circular dichroism, and fluorescence of 3,4-dihydroxyphenylalanine (Dopa) decarboxylase from pig kidney (pkDDC) was studied under equilibrium conditions. Unfolding proceeds in at least three stages. The first transition, occurring between 0 and 1 M GuCl, gives rise to a dimeric inactive species which has lost pyridoxal 5′-phosphate (PLP), and has a high tendency to aggregate, but retains almost all of the native spectroscopic characteristics. The second equilibrium transition, between 1 and 2.2 M GuCl, involves dimer dissociation, with some loss of tertiary and secondary structure. Additionally, gross conformational changes at or near the PLP microenvironment were detected by fluorescence of NaBH4-reduced enzyme. The third step, presumably representing complete unfolding of pkDDC, appears to be complete at 4.5 M GuCl, as indicated by the lack of further substantial changes in any of the signals being studied. Attempts at refolding resulted in the findings that: (1) partial reactivation is observed only starting from enzyme denatured at concentrations below 1.5 M GuCl, and (2) starting from completely denatured protein, the refolding process is apparently reversible down to concentrations of approx. 2 M GuCl. Taken together, this would seem to indicate that the monomer-dimer transition is impaired under the experimental conditions tested. A plausible model is presented for the unfolding/refolding of pkDDC.

Assigning in vivo carbamylation and acetylation in human lens proteins using tandem mass spectrometry and database searching

2007 ◽  
Vol 259 (1-3) ◽  
pp. 161-173 ◽  
Author(s):  
Zee-Yong Park ◽  
Rovshan Sadygov ◽  
Judy M. Clark ◽  
John I. Clark ◽  
John R. Yates
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Human Lens ◽  
Database Searching ◽  
Tandem Mass ◽  
Lens Proteins

Human Lens Proteins Examined by Immunochemical and Ultracentrifugal Techniques

1964 ◽  
Vol 72 (5) ◽  
pp. 660-666 ◽  
Author(s):  
A. L. duPREE ◽  
J. LITTLE ◽  
J. LANGMAN
Keyword(s):  
Human Lens ◽  
Lens Proteins
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