Related Experiment Video

Updated: Aug 3, 2026

Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
11:19

Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses

Published on: February 25, 2011

Microenvironment of cysteine 242 in type-1 ribosome-inactivating protein from iris

Q Hao1, E J Van Damme, A Barre

  • 1Laboratory of Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Willem de Croylaan 42, Leuven, 3001, Belgium.

Biochemical and Biophysical Research Communications
|August 31, 2000
PubMed

Insights

Iris ribosome-inactivating protein (IRIP) has a unique cysteine residue. This cysteine is accessible but not critical for IRIP’s RNA N-glycosidase activity, suggesting potential for novel immunotoxin development.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Chemistry

Background:

  • Iris ribosome-inactivating protein (IRIP) is a type-1 ribosome-inactivating protein (RIP) from Iris hollandica.
  • IRIP is notable for containing a cysteine residue, uncommon in type-1 RIPs.

Purpose of the Study:

  • To investigate the structural and functional significance of the unique cysteine residue (Cys242) in IRIP.
  • To assess the potential of IRIP as a novel immunotoxin.

Main Methods:

  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to assess protein aggregation.
  • Chemical modification using 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) to probe cysteine reactivity.
  • Molecular modeling to predict protein conformation.
  • Enzymatic activity assays to determine the effect of cysteine modification on RNA N-glycosidase activity.

Main Results:

  • SDS-PAGE revealed that IRIP can exist as disulfide-linked dimers.
  • Cys242 in IRIP is accessible but only partially reactive to thiol modifiers.
  • Ligand binding (adenine, poly(A)) did not significantly alter Cys242 conformation.
  • Chemical modification of Cys242 did not abolish IRIP's RNA N-glycosidase activity.

Conclusions:

  • The cysteine residue at position 242 in IRIP is not essential for its enzymatic function.
  • IRIP's unique cysteine residue's properties suggest potential for developing novel immunotoxins.

More Related Videos

Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs08:14

Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs

Published on: February 14, 2013

Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins11:25

Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins

Published on: October 4, 2017

Related Concept Videos

Termination of Translation01:44

Termination of Translation

The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through...
Riboswitches01:56

Riboswitches

Riboswitches are non-coding mRNA domains that regulate the transcription and translation of downstream genes without the help of proteins. Riboswitches bind directly to a metabolite and can form unique stem-loop or hairpin structures in response to the amount of the metabolite present. They have two distinct regions – a metabolite-binding aptamer and an expression platform.
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
Directing Proteins to the Rough Endoplasmic Reticulum01:34

Directing Proteins to the Rough Endoplasmic Reticulum

The organelle-specific signaling sequences direct proteins synthesized in the cytosol to their final destination like ER, mitochondria, peroxisomes, etc. Some of the proteins directed to ER are then trafficked via vesicles to other organelles within the cell or the extracellular environment through the Golgi complex. For example, the rough ER synthesizes soluble proteins for transportation to the lysosomes or secretion out of the cell. It can also synthesize transmembrane proteins that can...
Cotranslational Protein Translocation01:20

Cotranslational Protein Translocation

Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...