← Graph View All Domains
Biology › Genetics And Molecular Biology

Translation Elongation and Elongation Factors

College Depth 179 in the knowledge graph ☐ I know this ☆ Set as goal
Unlocks 1 downstream topic
translation elongation-factors ribosome protein-synthesis

Core Idea

During elongation, EF-Tu (prokaryotes) or eEF1A (eukaryotes) delivers aminoacyl-tRNA to the ribosomal A site in a GTP-dependent manner. GTP hydrolysis occurs upon correct codon-anticodon pairing (proofreading step). EF-G (prokaryotes) or eEF2 (eukaryotes) then catalyzes translocation of tRNAs and mRNA, advancing the ribosome by one codon.

How It's Best Learned

Use cryo-EM structures or animations to visualize the three-site model of the ribosome (A, P, E). Trace the movement of tRNAs and mRNA through successive cycles. Understand how GTP hydrolysis provides energy and ensures fidelity.

Common Misconceptions

Explainer

From your study of translation initiation, you know that the ribosome assembles on the mRNA with the initiator tRNA positioned in the P site (peptidyl site), base-paired with the start codon. The A site (aminoacyl site) is empty and ready to accept the next aminoacyl-tRNA. Elongation is the repetitive cycle that builds the polypeptide chain one amino acid at a time, and it proceeds through three distinct steps: codon-directed binding, peptide bond formation, and translocation.

In the first step, an aminoacyl-tRNA does not simply float into the A site on its own. Instead, the elongation factor EF-Tu (in prokaryotes) or eEF1A (in eukaryotes) delivers it in a complex with GTP. Think of EF-Tu as an escort with a security clearance — it brings the charged tRNA to the ribosome and holds it in position while the ribosome checks whether the anticodon matches the codon in the A site. If the match is correct, the geometry of the codon-anticodon interaction triggers a conformational change in the ribosome that stimulates GTP hydrolysis on EF-Tu. This is the proofreading step: the energy of GTP hydrolysis is used not to form the peptide bond itself, but to introduce a kinetic delay that gives incorrectly matched tRNAs time to dissociate before the irreversible step. Only after GTP hydrolysis and EF-Tu release is the aminoacyl-tRNA fully accommodated into the A site.

Once the correct aminoacyl-tRNA is in the A site, peptidyl transferase — an activity of the ribosomal RNA itself (making the ribosome a ribozyme) — catalyzes formation of a peptide bond between the amino acid on the A-site tRNA and the growing polypeptide chain attached to the P-site tRNA. The polypeptide is transferred from the P-site tRNA to the A-site tRNA, leaving a deacylated (empty) tRNA in the P site. At this point, the ribosome is in a hybrid state — the tRNAs have shifted relative to the large subunit but not yet relative to the small subunit.

The final step of each cycle is translocation, driven by the elongation factor EF-G (prokaryotes) or eEF2 (eukaryotes). EF-G binds the ribosome with GTP and, upon hydrolysis, physically moves the ribosome one codon down the mRNA. The deacylated tRNA shifts from the P site to the E site (exit site) and is released, the peptidyl-tRNA moves from A to P, and a new codon is exposed in the empty A site. The entire cycle then repeats — at a remarkable rate of about 15–20 amino acids per second in bacteria. Each elongation factor participates transiently: EF-Tu and EF-G bind, do their work, and dissociate within each cycle. EF-Tu is recharged by the exchange factor EF-Ts, which swaps GDP for GTP, readying EF-Tu for another round of tRNA delivery.

Practice Questions 5 questions

Prerequisite Chain

Counting to 10 → Counting to 20 → Understanding Zero → The Number Zero → Counting to Five → One-to-One Correspondence → Combining Small Groups Within 5 → Addition Within 10 → Addition Within 20 → Two-Digit Addition Without Regrouping → Two-Digit Addition with Regrouping → Addition Within 100 → Repeated Addition as Multiplication → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Two-Digit by One-Digit Division → Division with Remainders → Remainders and Quotients in Division → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Reading and Writing Decimals → Comparing and Ordering Decimals → Adding and Subtracting Decimals → Multiplying Decimals → Dividing Decimals → Dividing Fractions → Mixed Number Arithmetic → Order of Operations → Integer Order of Operations → Variable Expressions → Combining Like Terms → One-Step Equations → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Iterated Integrals and Fubini's Theorem → Double Integrals in Cartesian Coordinates → Double Integrals over Rectangular Regions → Double Integrals in Polar Coordinates → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Green's Theorem → Surface Integrals and Flux of Vector Fields → Surface Integrals and Flux of Vector Fields → Divergence Theorem: Flux and Outflow → Divergence Theorem → Electric Flux → Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → The Electromagnetic Spectrum → Blackbody Radiation and Planck's Law → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → Heisenberg Uncertainty Principle → Wavefunction and the Born Rule → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → Quantum Entanglement → Bell Theorem and Bell Inequalities → Postulates of Quantum Mechanics → Scattering Theory → Introduction to Scattering Theory → Partial Wave Analysis in Scattering → Spin Angular Momentum → Electron Spin and Intrinsic Magnetic Moment → Stern-Gerlach Experiment: Spin Quantization and Measurement → Electron Diffraction and Matter Wave Properties → Davisson-Germer Experiment: Crystal Diffraction of Electrons → Electron Diffraction and Matter Wave Interference → Wavefunctions and Probability Density Interpretation → Quantum Superposition and Linear Combinations of States → Quantum Operators and Observables → Canonical Commutation Relations and Uncertainty → Heisenberg Uncertainty Principle and Measurement Limits → Time-Independent Schrödinger Equation and Eigenvalues → Hydrogen Atom in Quantum Mechanics → Spectral Lines and Energy Transitions → Selection Rules for Atomic Transitions → LS and jj Coupling Schemes in Multi-Electron Atoms → Pauli Exclusion Principle and Antisymmetric Wavefunctions → Electron Configuration and the Aufbau Principle → The Periodic Table and Atomic Electronic Structure → The Periodic Table → Electron Configuration → Periodic Trends → Ionization Energy → Ionic Bonding → Lewis Structures → Resonance Structures and Delocalized Electrons → Resonance and Formal Charge → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Organic Reaction Mechanisms and Arrow Pushing → Electrophilic Addition to Alkenes → Aromaticity and Benzene → DNA Structure → Central Dogma of Molecular Biology → Transcription: DNA to RNA → RNA Types and Structure → RNA Processing and Splicing → Translation: RNA to Protein → Translation: Initiation and Elongation → Translation Initiation: Start Codons and Ribosomal Scanning → mRNA Translation Start Sites and Initiation → Ribosomal Initiation Factors and Initiator tRNA → Translation Elongation and Elongation Factors

Longest path: 180 steps · 785 total prerequisite topics

Prerequisites (2)

Ribosomal Initiation Factors and Initiator tRNAhard Translation Elongation and Termination: Peptide Bond Formationsoft

Leads To (1)

Translation Termination and Release Factorshard