Beta-internexin is a microtubule-associated protein identical to the 70-kDa heat-shock cognate protein and the clathrin uncoating ATPase.
We have examined the relationship of the ubiquitous 68-70-kDa cytoskeletal-associated protein beta-internexin (Napolitano, E. W., Pachter, J. S., Chin, S. S. M., and Liem, R. K. H. (1985) J. Cell Biol. 101, 1323-1331) to heat-shock cognate 70 (hsc70), the major constitutive member of the mammalian heat-shock protein 70 (hsp70) family of stress proteins. We purify beta-internexin from rat brain microtubules and confirm its identity with hsc70 and the clathrin-uncoating ATPase by the following criteria: 1) The partial sequence of a cyanogen bromide-derived peptide from beta-internexin matches the inferred amino acid sequence of the cDNA clone pRC62 encoding hsc70 from rat brain (O'Malley, K., Mauron, A., Barchas, J. D., and Kedes, L. (1985) Mol. Cell. Biol. 5, 3476-3483). 2) Mixing experiments followed by two-dimensional gel analyses reveal the precise co-migration of beta-internexin, the clathrin-uncoating ATPase, and the in vitro translation product of cDNA clone pHSP-4 encoding rat brain hsc70. 3) beta-Internexin is recognized by a monoclonal antibody reactive against the class of hsp70 proteins. 4) beta-Internexin purified from a microtubule-associated protein-enriched fraction of rat brain by virtue of high affinity binding to ATP-agarose possesses clathrin cage-specific ATPase activity.
Green
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LA
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Liem
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RK
D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D002966:Clathrin; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D015151:Immunoblotting; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D011506:Proteins / Q000302:isolation & purification; D051381:Rats
D000596:Amino Acids; D002352:Carrier Proteins; D002966:Clathrin; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C494373:Hspa8 protein, rat; D008869:Microtubule-Associated Proteins; D010446:Peptide Fragments; D011506:Proteins; D000251:Adenosine Triphosphatases