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Purification Of The Golgi Adenosine 3'-Phosphate 5'-Phosphosulfate Transporter, A Homodimer Within The Membrane, Elisabet Mandon, Marcos Milla, Ellis Kempner, Carlos Hirschberg
Purification Of The Golgi Adenosine 3'-Phosphate 5'-Phosphosulfate Transporter, A Homodimer Within The Membrane, Elisabet Mandon, Marcos Milla, Ellis Kempner, Carlos Hirschberg
Elisabet Mandon
Sulfation of proteoglycans, secretory and membrane proteins, and glycolipids occurs in the lumen of the Golgi apparatus. Adenosine 3'-phosphate 5'-phosphosulfate (PAPS), the sulfate donor in these reactions, must be transported from the cytosol, its site of synthesis, into the lumen of the Golgi apparatus. We have identified and purified to apparent homogeneity the rat liver Golgi membrane PAPS transporter by a combination of conventional and affinity chromatography as well as photoaffinity radiolabeling with adenosine 3',5'-bisphosphate, a competitive inhibitor of PAPS transport. The transporter, a 75-kDa protein, was purified 70,000-fold over homogenate (6% yield) and transported PAPS into phosphatidylcholine liposomes selectively …
The Integrin Alpha 6 Beta 4 Is A Laminin Receptor, Edward C. Lee, Margaret M. Lotz, Glenn D. Steele Jr., Arthur M. Mercurio
The Integrin Alpha 6 Beta 4 Is A Laminin Receptor, Edward C. Lee, Margaret M. Lotz, Glenn D. Steele Jr., Arthur M. Mercurio
Arthur M. Mercurio
In this study, the putative laminin receptor function of the alpha 6 beta 4 integrin was assessed. For this purpose, we used a human cell line, referred to as clone A, that was derived from a highly invasive, colon adenocarcinoma. This cell line, which expresses the alpha 6 beta 4 integrin, adheres to the E8 and not to the P1 fragment of laminin. The adhesion of clone A cells to laminin is extremely rapid with half-maximal adhesion observed at 5 min after plating. Adhesion to laminin is blocked by GoH3, and alpha 6 specific antibody (60% inhibition), as well as …
A Membrane Cytoskeleton From Dictyostelium Discoideum. Ii. Integral Proteins Mediate The Binding Of Plasma Membranes To F-Actin Affinity Beads, Elizabeth J. Luna, C. M. Goodloe-Holland, H. M. Ingalls
A Membrane Cytoskeleton From Dictyostelium Discoideum. Ii. Integral Proteins Mediate The Binding Of Plasma Membranes To F-Actin Affinity Beads, Elizabeth J. Luna, C. M. Goodloe-Holland, H. M. Ingalls
Elizabeth J. Luna
In novel, low-speed sedimentation assays, highly purified, sonicated Dictyostelium discoideum plasma membrane fragments bind to F-actin beads (fluorescein-labeled F-actin on antifluorescein IgG-Sephacryl S-1000 beads). Binding was found to be (a) specific, since beads containing bound fluorescein-labeled ovalbumin or beads without bound fluorescein-labeled protein do not bind membranes, (b) saturable at approximately 0.6 microgram of membrane protein per microgram of bead-bound F-actin, (c) rapid with a t1/2 of 4-20 min, and (d) apparently of reasonable affinity since the off rate is too slow to be measured by present techniques. Using low-speed sedimentation assays, we found that sonicated plasma membrane fragments, after …
Direct Binding Of F-Actin To Ponticulin, An Integral Plasma Membrane Glycoprotein, C. Chia, Anne Hitt, Elizabeth Luna
Direct Binding Of F-Actin To Ponticulin, An Integral Plasma Membrane Glycoprotein, C. Chia, Anne Hitt, Elizabeth Luna
Elizabeth J. Luna
We have developed an 125I-labeled F-actin blot overlay assay for the identification of F-actin-binding proteins after transfer to nitrocellulose from SDS-polyacrylamide gels. Two major F-actin-binding proteins from Dictyostelium discoideum, a cytoplasmic 30 kDa protein and a 17 kDa integral membrane protein, and two minor membrane polypeptides of 19 kDa and 15 kDa were detected by this method. Using F-actin affinity and immunoaffinity chromatography, the 17 kDa polypeptide was identified as ponticulin, a previously described actin-binding glycoprotein from D. discoideum plasma membranes (Wuestehube, L.J., and Luna, E.J., [1987]: J. Cell Biol. 105:1741-1751). The binding of F-actin to ponticulin on blots is …
A Stable, High Capacity, F-Actin Affinity Column, Elizabeth Luna, Y. Wang, E. Voss, D. Branton, D. Taylor
A Stable, High Capacity, F-Actin Affinity Column, Elizabeth Luna, Y. Wang, E. Voss, D. Branton, D. Taylor
Elizabeth J. Luna
A high capacity F-actin affinity matrix is constructed by binding fluorescyl-actin to rabbit anti-fluorescein IgG that is covalently bound to Sepharose 4B. When stabilized with phalloidin, the actin remains associated with the Sepharose beads during repeated washes, activates the ATPase activity of myosin subfragment 1, and specifically binds 125I-heavy meromyosin and 125I-tropomyosin. The associations between the F-actin affinity matrix and the iodinated F-actin binding proteins are monitored both by affinity chromatography and by a rapid, low speed sedimentation assay. Anti-fluorescein IgG-Sepharose should be generally useful as a matrix for the immobilization of proteins containing accessible, covalently bound fluorescein groups.
F-Actin Binds To The Cytoplasmic Surface Of Ponticulin, A 17-Kd Integral Glycoprotein From Dictyostelium Discoideum Plasma Membranes, L. J. Wuestehube, Elizabeth J. Luna
F-Actin Binds To The Cytoplasmic Surface Of Ponticulin, A 17-Kd Integral Glycoprotein From Dictyostelium Discoideum Plasma Membranes, L. J. Wuestehube, Elizabeth J. Luna
Elizabeth J. Luna
F-actin affinity chromatography and immunological techniques are used to identify actin-binding proteins in purified Dictyostelium discoideum plasma membranes. A 17-kD integral glycoprotein (gp17) consistently elutes from F-actin columns as the major actin-binding protein under a variety of experimental conditions. The actin-binding activity of gp17 is identical to that of intact plasma membranes: it resists extraction with 0.1 N NaOH, 1 mM dithiothreitol (DTT); it is sensitive to ionic conditions; it is stable over a wide range of pH; and it is eliminated by proteolysis, denaturation with heat, or treatment with DTT and N-ethylmaleimide. gp17 may be responsible for much of …