Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 288, Issue 39, Pages 28009-28020Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M113.501346
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Funding
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2009/10875-9, 2010/05003-0, 2012/14298-9, 2010/05987-0, 2011/06654-7, 2009/54067-3]
- Laboratorio Nacional de Biociencias
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [10/05003-0, 10/05987-0, 09/54067-3, 11/06654-7] Funding Source: FAPESP
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The phosphate-dependent transition between enzymatically inert dimers into catalytically capable tetramers has long been the accepted mechanism for the glutaminase activation. Here, we demonstrate that activated glutaminase C(GAC) self-assembles into a helical, fiber-like double-stranded oligomer and propose a molecular model consisting of seven tetramer copies per turn per strand interacting via the N-terminal domains. The loop (LRFNKL326)-L-321 is projected as the major regulating element for self-assembly and enzyme activation. Furthermore, the previously identified in vivo lysine acetylation (Lys(311) in humans, Lys(316) in mouse) is here proposed as an important down-regulator of superoligomer assembly and protein activation. Bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl) ethyl sulfide, a known glutaminase inhibitor, completely disrupted the higher order oligomer, explaining its allosteric mechanism of inhibition via tetramer stabilization. A direct correlation between the tendency to self-assemble and the activity levels of the three mammalian glutaminase isozymes was established, with GAC being the most active enzyme while forming the longest structures. Lastly, the ectopic expression of a fiber-prone superactive GAC mutant in MDA-MB 231 cancer cells provided considerable proliferative advantages to transformed cells. These findings yield unique implications for the development of GAC-oriented therapeutics targeting tumor metabolism.
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