scholarly journals Lead-Binding Proteins: A Review

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Harvey C. Gonick
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Aminolevulinic Acid ◽  
Binding Capacity ◽  
Binding Protein ◽  
Protein A ◽  
Blood Lead ◽  
Low Molecular Weight ◽  
Acid Dehydratase ◽  
Low Molecular Weight Proteins

Lead-binding proteins are a series of low molecular weight proteins, analogous to metallothionein, which segregate lead in a nontoxic form in several organs (kidney, brain, lung, liver, erythrocyte). Whether the lead-binding proteins in every organ are identical or different remains to be determined. In the erythrocyte, delta-aminolevulinic acid dehydratase (ALAD) isoforms have commanded the greatest attention as proteins and enzymes that are both inhibitable and inducible by lead. ALAD-2, although it binds lead to a greater degree than ALAD-1, appears to bind lead in a less toxic form. What may be of greater significance is that a low molecular weight lead-binding protein, approximately 10 kDa, appears in the erythrocyte once blood lead exceeds 39 μg/dL and eventually surpasses the lead-binding capacity of ALAD. In brain and kidney of environmentally exposed humans and animals, a cytoplasmic lead-binding protein has been identified as thymosinβ4, a 5 kDa protein. In kidney, but not brain, another lead-binding protein has been identified as acyl-CoA binding protein, a 9 kDa protein. Each of these proteins, when coincubated with liver ALAD and titrated with lead, diminishes the inhibition of ALAD by lead, verifying their ability to segregate lead in a nontoxic form.

Rap1b Association with the Platelet Cytoskeleton Occurs in the Absence of Glycoproteins IIb/IIIa

1998 ◽  
Vol 79 (04) ◽  
pp. 832-836 ◽  
Author(s):  
Thomas Fischer ◽  
Christina Duffy ◽  
Gilbert White
Keyword(s):  
Molecular Weight ◽  
Divalent Cation ◽  
Binding Proteins ◽  
Binding Protein ◽  
Platelet Membrane ◽  
Low Molecular Weight ◽  
Membrane Glycoproteins ◽  
Gtp Binding Protein ◽  
Gtp Binding Proteins ◽  
Gtp Binding

SummaryPlatelet membrane glycoproteins (GP) IIb/IIIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann’s thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and rap1b is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.

Plasma clearance of chicken and human insulin-like growth factor-I and their association with circulating binding proteins in chickens

1990 ◽  
Vol 124 (3) ◽  
pp. 361-370 ◽  
Author(s):  
G. L. Francis ◽  
J. P. McMurtry ◽  
R. J. Johnson ◽  
F. J. Ballard
Keyword(s):  
Molecular Weight ◽  
Growth Factor ◽  
Binding Proteins ◽  
Degradation Products ◽  
Binding Protein ◽  
Low Molecular Weight ◽  
Plasma Samples ◽  
Factor I ◽  
Gel Permeation ◽  
Igf I

ABSTRACT We have investigated the clearance of 125I-labelled chicken and recombinant human insulin-like growth factor-I (IGF-I) from the circulation of chickens as well as the role that IGF-binding proteins play in this process. Analysis of plasma samples by high-performance liquid chromatography (HPLC) neutral gel permeation on a TSK G3000SW column indicated that the i.v. injected radioactivity was rapidly partitioned between at least three pools. Most of the radioactivity occurred in a complex with binding protein(s), while smaller amounts of radioactivity chromatographed in the free IGF-I peak or appeared as low molecular weight degradation products. The labelled chicken and human IGF-I were rapidly cleared during the first 90 min. The calculated half-life for total labelled IGF-I during this period was 54 min for the chicken tracer and 33 min for the human tracer. The clearance was monitored for 10 h during which the human tracer continued to be cleared more rapidly than the chicken tracer. The proportion of radioactivity appearing as low molecular weight degradation products increased with time. Acid gel permeation and reverse-phase HPLC of the binding protein-associated radioactivity demonstrated that the labelled IGF-I bound was intact IGF-I. Sephadex G-200 gel permeation chromatography of chicken plasma samples at pH 7·4 showed that the binding protein complex labelled in vivo with chicken IGF-I tracer had a molecular mass of 55 kDa. Furthermore, the tracer associated with the binding protein coeluted with the major peak of endogenous IGF-I, suggesting that the tracer was bound to the physiologically relevant binding protein. Similar results were obtained with Superose 12 chromatography. Human plasma chromatographed as expected with much of the immunoreactivity and the labelled IGF-I eluting with a mass of 150 kDa on both Sephadex G-200 and Superose 12 columns. Ligand blotting of plasma binding proteins with 125I-labelled IGF-I after first subjecting the samples to polyacrylamide gel electrophoresis and transfer to nitrocellulose confirmed that the predominant binding protein in chicken plasma differed from the major forms in human plasma. Journal of Endocrinology (1990) 124, 361–370

Light-chain binding sites on renal brush-border membranes

1990 ◽  
Vol 258 (5) ◽  
pp. F1259-F1265 ◽  
Author(s):  
V. Batuman ◽  
A. W. Dreisbach ◽  
J. Cyran
Keyword(s):  
Molecular Weight ◽  
Light Chain ◽  
Brush Border ◽  
Binding Sites ◽  
Binding Capacity ◽  
Light Chains ◽  
Low Molecular Weight ◽  
Brush Border Membranes ◽  
Proximal Tubular ◽  
Low Molecular Weight Proteins

Immunoglobulin light chains are low-molecular-weight proteins filtered at the renal glomerulus and catabolized within the proximal tubular epithelium. Excessive production and urinary excretion of light chains are associated with renal dysfunction. They also interfere with proximal renal tubule epithelial functions in vitro. We studied the binding of 125I-labeled kappa- and lambda-light chains, obtained from the urine of multiple myeloma patients, to rat and human renal proximal tubular brush-border membranes. Light-chain binding to brush borders was also demonstrated immunologically by flow cytometry. Computer analysis of binding data was consistent with presence of a single class of low-affinity, high-capacity, non-cooperative binding sites with relative selectivity for light chains on both rat and human kidney brush-border membranes. The dissociation constants of light chains ranged from 1.6 X 10(-5) to 1.2 X 10(-4) M, and maximum binding capacity ranged from 4.7 +/- 1.3 X 10(-8) to 8.0 +/- 0.9 X 10(-8) (SD) mol/mg protein at 25 degrees C. Kappa- and lambda-light chains competed with each other for binding with comparable affinity constants. Competition by albumin and beta-lactoglobulin, however, was much weaker, suggesting relative site selectivity for light chains. These binding sites probably function as endocytotic receptors for light chains and possibly other low-molecular-weight proteins.

Inhibition of Copper-Associated Erythrocyte Ghost Membrane Lipid Peroxidation by Hepatic Cytosolic Low Molecular Weight Proteins

1991 ◽  
Vol 19 (3) ◽  
pp. 206-213
Author(s):  
Bruce L. Homer ◽  
Kenneth R. Pierce ◽  
Charles H. Bridges ◽  
James E. Womack ◽  
Blair A. Sowa ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Molecular Weight ◽  
Membrane Lipid ◽  
Erythrocyte Ghost ◽  
Low Molecular Weight ◽  
Membrane Lipid Peroxidation ◽  
Low Molecular Weight Proteins

Zinc- and copper-binding proteins in the plasma of winter flounder (Pseudopleuronectes americanus)

1980 ◽  
Vol 58 (4) ◽  
pp. 609-613 ◽  
Author(s):  
P. E. Fletcher ◽  
G. L. Fletcher
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Binding Protein ◽  
Gel Filtration ◽  
Protein S ◽  
Egg Yolk ◽  
Winter Flounder ◽  
Zinc Binding ◽  
Copper Binding ◽  
Copper Binding Proteins

Zinc- and copper-binding proteins were isolated from the plasma of winter flounder using gel filtration chromatography. A single copper-binding protein fraction of molecular weight 170 000 was isolated from the plasma of both sexes.In male and female flounder over 95% of the plasma zinc was associated with a zinc-binding protein(s) with a molecular weight of 76 000. In male flounder the remaining zinc appeared to be bound to a protein(s) of molecular weight 186 000. In female flounder the remaining 5% of the zinc was associated with two zinc-binding fractions with apparent molecular weights of 186 000 and 340 000 – 370 000.Extracts of plasma vitellogenin and egg yolk proteins revealed significant quantities of zinc and copper. It is hypothesized that the female specific zinc-binding protein (340 000 – 370 000) was vitellogenin.

Sign in / Sign up

Export Citation Format

Share Document