scholarly journals Small GTP-Binding Proteins on Rat Liver Lysosomal Membranes.

1992 ◽  
Vol 17 (6) ◽  
pp. 363-369 ◽  
Author(s):  
Yoshimichi Sai ◽  
Shoji Ohkuma
Keyword(s):  
Rat Liver ◽  
Binding Proteins ◽  
Gtp Binding Proteins ◽  
Lysosomal Membranes ◽  
Gtp Binding

scholarly journals Detection of GTP-binding proteins in purified derivatives of rough endoplasmic reticulum

1989 ◽  
Vol 262 (2) ◽  
pp. 497-503 ◽  
Author(s):  
J Lanoix ◽  
L Roy ◽  
J Paiement
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Rough Endoplasmic Reticulum ◽  
Binding Proteins ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cell Types ◽  
Electrophoretic Analysis ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Dog Pancreas

As a first step in determining the molecular mechanism of membrane fusion stimulated by GTP in rough endoplasmic reticulum (RER), we have looked for GTP-binding proteins. Rough microsomes from rat liver were treated for the release of ribosomes, and the membrane proteins were separated by SDS/polyacrylamide-gel electrophoresis. The polypeptides were then blotted on to nitrocellulose sheets and incubated with [alpha-32P]GTP [Bhullar & Haslam (1987) Biochem. J. 245, 617-620]. A doublet of polypeptides (23 and 24 kDa) was detected in the presence of 2 microM-MgCl2. Binding of [alpha-32P]GTP was blocked by 1-5 mM-EDTA, 10-10,000 nM-GTP or 10 microM-GDP. Either guanosine 5′-[gamma-thio]triphosphate or guanosine 5′-[beta gamma-imido]triphosphate at 100 nM completely inhibited binding, but ATP, CTP or UTP at 10 mciroM did not. Pretreatment of microsomes by mild trypsin treatment (0.5-10 micrograms of trypsin/ml, concentrations known not to affect microsomal permeability) led to inhibition of [alpha-32P]GTP binding, suggesting a cytosolic membrane orientation for the GTP-binding proteins. Two-dimensional gel-electrophoretic analysis revealed the 23 and 24 kDa [alpha-32P]GTP-binding proteins to have similar acid isoelectric points. [alpha-32P]GTP binding occurred to similar proteins of rough microsomes from rat liver, rat prostate and dog pancreas, as well as to a 23 kDa protein of rough microsomes from frog liver, but occurred to distinctly different proteins in a rat liver plasma-membrane-enriched fraction. Thus [alpha-32P]GTP binding has been demonstrated to two low-molecular-mass (approx. 21 kDa) proteins in the rough endoplasmic reticulum of several varied cell types.

scholarly journals Distribution of polypeptides binding guanosine 5′-[γ-[35S]thio]triphosphate and anti-(ras protein) antibodies in liver subcellular fractions. Evidence for endosome-specific components

1990 ◽  
Vol 271 (1) ◽  
pp. 179-183 ◽  
Author(s):  
N Ali ◽  
W H Evans
Keyword(s):  
Rat Liver ◽  
Subcellular Distribution ◽  
Plasma Membranes ◽  
Binding Proteins ◽  
Subcellular Fractions ◽  
Relative Distribution ◽  
Ras Proteins ◽  
Ras Protein ◽  
Gtp Binding Proteins ◽  
Gtp Binding

The subcellular distribution in rat liver of polypeptides binding guanosine 5′-[gamma-[35S]thio]triphosphate [( 35S]GTP[S]) and seven antibodies against ras oncoproteins was evaluated. Multiple low-Mr (21,000-28,000) GTP-binding proteins were detected, but their relative distribution among the membrane fractions varied. A more specific compartmentation of polypeptides which bind antibodies generated against ras proteins was evident, with an Mr-28,000 polypeptide and a probable Mr-56,000 dimer, identified by six of the antibodies tested, being confined mainly to endosomes. An Mr-23,000 polypeptide was detected by some of the antibodies in all of the membrane fractions, but especially in the plasma membranes.

scholarly journals GTP-binding proteins in rat liver nuclear envelopes.

1990 ◽  
Vol 87 (18) ◽  
pp. 7080-7084 ◽  
Author(s):  
J B Rubins ◽  
J O Benditt ◽  
B F Dickey ◽  
N Riedel
Keyword(s):  
Rat Liver ◽  
Binding Proteins ◽  
Gtp Binding Proteins ◽  
Gtp Binding

scholarly journals Rat liver GTP-binding proteins mediate changes in mitochondrial membrane potential and organelle fusion

1999 ◽  
Vol 276 (3) ◽  
pp. C611-C620 ◽  
Author(s):  
Jorge Daniel Cortese
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Binding Proteins ◽  
Mitochondrial Fusion ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Gtp Binding Proteins ◽  
Gtp Binding

The variety of mitochondrial morphology in healthy and diseased cells can be explained by regulated mitochondrial fusion. Previously, a mitochondrial outer membrane fraction containing fusogenic, aluminum fluoride (AlF4)-sensitive GTP-binding proteins (mtg) was separated from rat liver (J. D. Cortese, Exp. Cell Res. 240: 122–133, 1998). Quantitative confocal microscopy now reveals that mtg transiently increases mitochondrial membrane potential (ΔΨ) when added to permeabilized rat hepatocytes (15%), rat fibroblasts (19%), and rabbit myocytes (10%). This large mtg-induced ΔΨ increment is blocked by fusogenic GTPase-specific modulators such as guanosine 5′- O-(3-thiotriphosphate), excess GTP (>100 μM), and AlF4, suggesting a linkage between ΔΨ and mitochondrial fusion. Accordingly, stereometric analysis shows that decreasing ΔΨ or ATP synthesis with respiratory inhibitors limits mtg- and AlF4-induced mitochondrial fusion. Also, a specific G protein inhibitor ( Bordetella pertussis toxin) hyperpolarizes mitochondria and leads to a loss of AlF4-dependent mitochondrial fusion. These results place mtg-induced ΔΨ changes upstream of AlF4-induced mitochondrial fusion, suggesting that GTPases exert ΔΨ-dependent control of the fusion process. Mammalian mitochondrial morphology thus can be modulated by cellular energetics.

Small GTP-binding Protein RalA Associates with Weibel-Palade Bodies in Endothelial Cells

1999 ◽  
Vol 82 (09) ◽  
pp. 1177-1181 ◽  
Author(s):  
Hubert de Leeuw ◽  
Pauline Wijers-Koster ◽  
Jan van Mourik ◽  
Jan Voorberg
Keyword(s):  
Endothelial Cells ◽  
Binding Proteins ◽  
Binding Protein ◽  
Control Release ◽  
Small Gtpase ◽  
Gtp Binding Protein ◽  
Two Dimensional Gel Electrophoresis ◽  
Gtp Binding Proteins ◽  
Dense Granules ◽  
Gtp Binding

SummaryIn endothelial cells von Willebrand factor (vWF) and P-selectin are stored in dense granules, so-called Weibel-Palade bodies. Upon stimulation of endothelial cells with a variety of agents including thrombin, these organelles fuse with the plasma membrane and release their content. Small GTP-binding proteins have been shown to control release from intracellular storage pools in a number of cells. In this study we have investigated whether small GTP-binding proteins are associated with Weibel-Palade bodies. We isolated Weibel-Palade bodies by centrifugation on two consecutive density gradients of Percoll. The dense fraction in which these subcellular organelles were highly enriched, was analysed by SDS-PAGE followed by GTP overlay. A distinct band with an apparent molecular weight of 28,000 was observed. Two-dimensional gel electrophoresis followed by GTP overlay revealed the presence of a single small GTP-binding protein with an isoelectric point of 7.1. A monoclonal antibody directed against RalA showed reactivity with the small GTP-binding protein present in subcellular fractions that contain Weibel-Palade bodies. The small GTPase RalA was previously identified on dense granules of platelets and on synaptic vesicles in nerve terminals. Our observations suggest that RalA serves a role in regulated exocytosis of Weibel-Palade bodies in endothelial cells.

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.

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