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Related Concept Videos

Amino Acid Biosynthetic Pathways01:29

Amino Acid Biosynthetic Pathways

Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which provide...
Transcription Attenuation in Prokaryotes02:42

Transcription Attenuation in Prokaryotes

Transcriptional attenuation occurs when RNA transcription is prematurely terminated due to the formation of a terminator mRNA hairpin structure.  Bacteria use these hairpins to regulate the transcription process and control the synthesis of several amino acids including histidine, lysine, threonine, and phenylalanine. Transcription attenuation takes place in the non-coding regions of mRNA.
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
Electron Transport Chain Components01:29

Electron Transport Chain Components

The electron transport chain (ETC) is a crucial metabolic pathway that facilitates energy conversion in prokaryotic and eukaryotic cells. In eukaryotes, the ETC comprises four membrane-associated protein complexes in the inner mitochondrial membrane. In prokaryotes, the ETC in the plasma membrane can vary in composition, with fewer or different complexes depending on the organism and environmental conditions. These complexes transfer electrons from electron donors, such as NADH and FADH2, to...
Protein Transport to the Thylakoids01:22

Protein Transport to the Thylakoids

Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
Energy to Drive Translocation01:37

Energy to Drive Translocation

Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...

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Related Experiment Video

Updated: Jul 4, 2026

Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol
08:33

Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol

Published on: September 21, 2021

Tryptophan-accelerated electron flow through proteins.

Crystal Shih1, Anna Katrine Museth, Malin Abrahamsson

  • 1Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.

Science (New York, N.Y.)
|June 28, 2008
PubMed
Summary

Biological charge transport is enhanced by multistep electron tunneling. A tryptophan residue significantly speeds up electron transfer between metal redox centers in Pseudomonas aeruginosa azurin.

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PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
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PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase

Published on: September 26, 2020

Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET
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Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET

Published on: October 9, 2021

Related Experiment Videos

Last Updated: Jul 4, 2026

Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol
08:33

Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol

Published on: September 21, 2021

PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
09:31

PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase

Published on: September 26, 2020

Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET
12:07

Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET

Published on: October 9, 2021

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Spectroscopy

Background:

  • Biological energy flow relies on efficient charge transport over long molecular distances.
  • Multistep electron tunneling, mediated by redox-active amino acids, can enhance charge-transfer rates.

Purpose of the Study:

  • To quantify the role of an intervening tryptophan residue in facilitating electron transfer between distant metal redox centers.
  • To investigate electron transfer mechanisms in a mutant Pseudomonas aeruginosa azurin.

Main Methods:

  • Transient optical spectroscopy
  • Infrared spectroscopy
  • Kinetics modeling
  • Site-directed mutagenesis of Pseudomonas aeruginosa azurin

Main Results:

  • Electron transfer between Cu(I) and a photoexcited Re(I)-diimine occurred in nanoseconds.
  • This rate was two orders of magnitude faster than predicted for single-step tunneling over a 19 angstrom distance.
  • The tryptophan residue at position 122 significantly facilitated the electron transfer process.

Conclusions:

  • Intervening redox-active amino acids, like tryptophan, can dramatically enhance biological charge transport rates.
  • Multistep electron tunneling is a viable mechanism for efficient long-range electron transfer in proteins.
  • This finding has implications for understanding energy flow in biological systems.