#GTP hydrolysis

Cytoskeleton

What is the role of GTP hydrolysis in microtubule assembly?

Microtubules do not require GTP hydrolysis to polymerize hydrolysis follows incorporation and modulates stability rather than providing assembly energy which is entropically driven. After alpha beta dimer carrying GTP on beta adds to plus end longitudinal contacts induce GTPase activity converting beta bound GTP to GDP plus inorganic phosphate retained initially as GDP Pi lattice. GDP tubulin prefers bent conformation by about 12 degrees but constrained straight within wall creating mechanical strain stored as elastic energy. As long as terminal layers retain GTP cap maintains stabilizing infl

Ref: Desai & Mitchison, Annu Rev Cell Dev Biol 1997 – GTP hydrolysis causing depolymerization and catastrophe timer.

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Protein Sorting and Trafficking

The major energy source for nuclear transport is:

Energy input driving selective accumulation of proteins inside nucleus does not come from kinesin ATP hydrolysis used for microtubule transport or proton motive force powering mitochondrial import, but from compartmentalized GTP turnover of Ran. RCC1 guanine exchange factor bound to nucleosomes continuously recharges Ran-GDP to Ran-GTP using nuclear GTP pool, while cytoplasmic RanGAP1 SUMOylated and anchored to RanBP2/Nup358 plus co-activator RanBP1 hydrolyze GTP outside. Each import cycle consumes one GTP upon export complex disassembly in cytosol, and each export cycle consumes GTP as Ran-GT

Ref: NCBI Bookshelf, Molecular Biology of the Cell, Section: GTP Hydrolysis by Ran as Energy Source.

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Cell Signaling GPCR Pathways - I

Primary role of GTPase activity of Gα is

signal termination, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling Fundamental PrinciplesI

GAP inactivates Ras by

hydrolyzing GTP, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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