GTP/GDP (Signal-Switch Oscillation)
GTP/GDP is the τ-categorical signal-switch oscillation: a two-state cycle structurally homologous to ATP/ADP but specialized for information rather than bulk energy transduction. It powers protein synthesis (translation factors), signal transduction (G-proteins, small GTPases), and cytoskeletal dynamics (tubulin, septins). It is the signaling-axis instantiation of the universal currency template VI.D32.
τ-Definition
GTP/GDP is the τ-categorical signal-switch oscillation: a two-state cycle structurally homologous to ATP/ADP but specialized for information rather than bulk energy transduction. It powers protein synthesis (translation factors), signal transduction (G-proteins, small GTPases), and cytoskeletal dynamics (tubulin, septins). It is the signaling-axis instantiation of the universal currency template VI.D32.
Categorical invariant. Two-state τ-categorical oscillation: GDP + P_i ⇌ GTP, with ΔG ≈ -7 kcal/mol per hydrolysis (matching ATP within thermodynamic error); used as an irreversibility lock for binary on/off switches rather than for bulk anabolic coupling.
Primary registry anchor:
VI.D32
τ-Derivation Chain
-
I.K0— Universe Postulate -
VI.D15— Life Sector -
VI.D31— Metabolic Circulation -
VI.T09— Metabolism = Life Loop Class -
VI.P11— Krebs Cycle as Loop_L instantiation — substrate-level GTP synthesis at succinyl-CoA synthetase -
VI.D32— ATP/ADP Oscillation — GTP/GDP is the signaling-axis instance of the same currency template
Empirical Correlate
Biomarker: Cellular [GTP] ≈ 0.3-0.5 mM (10× lower than ATP); GTP/GDP ratio ≈ 4-10 in resting cells; ΔG of GTP hydrolysis ≈ -7 kcal/mol (within experimental uncertainty of ATP); active-state lifetime of typical small GTPase (Ras, Rab, Rho) ≈ 10⁻¹-10² s, set by GAP-stimulated hydrolysis.
Measurable range: GTP turnover during protein synthesis: ~4 GTP per peptide bond (EF-Tu·GTP, EF-G·GTP, IF/RF cycles); microtubule dynamic instability: tubulin-GTP cap ~50-300 dimers, hydrolysis rate ~0.25 s⁻¹; G-protein activation cycle ~10-100 ms (visual transduction) to seconds (hormonal).
Observation method: HPLC of nucleotide pool, GTP-binding pulldown with GST-RBD (active Ras / Rho / Rac), FRET biosensors (Raichu series), GAP / GEF in-vitro assays, single-molecule TIRF of fluorescent-GTP analogs (mant-GTP, BODIPY-GTP).
Calibration anchor: LG-Y02-kinetic-pseudoscalar-channel
Anchor chain:
- VI.L18 chirality channel
- D-ribose handedness in GTP guanosine sugar
- stereospecific GTPase switch I/II loop conformations
Manuscript reference: manuscript-sources/book-06/part03/ch20-atp.tex
Lean Coverage
Status: Planned