Activation of human VPS4A by ESCRT-III proteins reveals ability of substrates to relieve enzyme autoinhibition.
J Biol Chem
; 285(46): 35428-38, 2010 Nov 12.
Article
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| MEDLINE
| ID: mdl-20805225
ABSTRACT
VPS4 proteins are AAA(+) ATPases required to form multivesicular bodies, release viral particles, and complete cytokinesis. They act by disassembling ESCRT-III heteropolymers during or after their proposed function in membrane scission. Here we show that purified human VPS4A is essentially inactive but can be stimulated to hydrolyze ATP by ESCRT-III proteins in a reaction that requires both their previously defined MIT interacting motifs and â¼50 amino acids of the adjacent sequence. Importantly, C-terminal fragments of all ESCRT-III proteins tested, including CHMP2A, CHMP1B, CHMP3, CHMP4A, CHMP6, and CHMP5, activated VPS4A suggesting that it disassembles ESCRT-III heteropolymers by affecting each component protein. VPS4A is thought to act as a ring-shaped cylindrical oligomer like other AAA(+) ATPases, but this has been difficult to directly demonstrate. We found that concentrating His(6)-VPS4A on liposomes containing Ni(2+)-nitrilotriacetic acid-tagged lipid increased ATP hydrolysis, confirming the importance of inter-subunit interactions for activity. We also found that mutating pore loops expected to line the center of a cylindrical oligomer changed the response of VPS4A to ESCRT-III proteins. Based on these data, we propose that ESCRT-III proteins facilitate assembly of functional but transient VPS4A oligomers and interact with sequences inside the pore of the assembled enzyme. Deleting the N-terminal MIT domain and adjacent linker from VPS4A increased both basal and liposome-enhanced ATPase activity, indicating that these elements play a role in autoinhibiting VPS4A until it encounters ESCRT-III proteins. These findings reveal new ways in which VPS4 activity is regulated and specifically directed to ESCRT-III polymers.
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MEDLINE
Asunto principal:
Adenosina Trifosfato
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Adenosina Trifosfatasas
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Secuencias de Aminoácidos
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Complejos de Clasificación Endosomal Requeridos para el Transporte
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
2010
Tipo del documento:
Article
País de afiliación:
Estados Unidos