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Publication Abstract from PubMed

The phosphate-dependent transition between enzimatically 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 L321RFNKL326 is projected as the major regulating element for self-assembly and enzyme activation. Furthermore, the previously identified in vivo lysine acetylation (Lys311 in humans, Lys316 in mouse) is here proposed as an important down-regulator of super-oligomer assembly and protein activation. BPTES (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 more active enzyme while forming the longest structures. Lastly, the ectopic expression of a fiber-prone super-active 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.

Active Glutaminase C self-assembles into a supra-tetrameric oligomer which can be disrupted by an allosteric inhibitor.,Ferreira AP, Cassago A, Goncalves KA, Dias MM, Adamoski D, Ascencao CF, Honorato RV, de Oliveira JF, Ferreira IM, Fornezari C, Bettini J, Oliveira PS, Paes Leme AF, Portugal RV, Ambrosio AL, Dias SM J Biol Chem. 2013 Aug 8. PMID:23935106^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.