Related Experiment Video

Updated: May 22, 2026

Combining X-Ray Crystallography with Small Angle X-Ray Scattering to Model Unstructured Regions of Nsa1 from S. Cerevisiae
09:15

Combining X-Ray Crystallography with Small Angle X-Ray Scattering to Model Unstructured Regions of Nsa1 from S. Cerevisiae

Published on: January 10, 2018

Structural insights into the assembly and shape of Type III restriction-modification (R-M) EcoP15I complex by

Yogesh K Gupta1, Lin Yang, Siu-Hong Chan

  • 1Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA.

Journal of Molecular Biology
|May 8, 2012
PubMed

Insights

Structural insights into EcoP15I, a Type III restriction enzyme, reveal its holoenzyme

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Background:

  • EcoP15I is a Type III restriction enzyme crucial for DNA modification and cleavage.
  • Understanding its structure is key to elucidating its enzymatic mechanism.
  • Previous studies lacked structural data for Type III restriction enzymes.

Purpose of the Study:

  • To determine the overall structure of the EcoP15I holoenzyme and its Mod(2) subcomplex.
  • To provide structural basis for the enzyme's DNA interaction and cleavage mechanism.

Main Methods:

  • Small-angle X-ray scattering (SAXS) was employed to analyze the enzyme's shape and dimensions.
  • Analytical ultracentrifugation provided further biophysical characterization.
  • SAXS data were used to reconstruct low-resolution envelopes of the enzyme complexes.

Main Results:

  • The Mod(2) subcomplex exhibits a compact structure (R(G) ~37.4 Å, Dmax ~110 Å).
  • The EcoP15I holoenzyme adopts an elongated crescent shape (R(G) ~65.3 Å, Dmax ~218 Å).
  • A structural model suggests the Mod(2) subcomplex is centrally located, flanked by Res subunits.

Conclusions:

  • The proposed model supports a mechanism where Res subunits form a sliding clamp around DNA.
  • This structural information advances our understanding of Type III restriction enzyme function.
  • Further studies can build upon these findings to explore enzyme regulation and activity.

More Related Videos

Structural Studies of Macromolecules in Solution using Small Angle X-Ray Scattering07:19

Structural Studies of Macromolecules in Solution using Small Angle X-Ray Scattering

Published on: November 5, 2018

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies10:01

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies

Published on: November 28, 2017

Related Concept Videos

Protein Complex Assembly02:41

Protein Complex Assembly

Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.  Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
Many viruses self-assemble into a fully functional unit using the infected host cell to...
Restriction Enzymes01:11

Restriction Enzymes

Restriction enzymes are bacterial enzymes used to cut DNA in a sequence-specific manner. To cleave DNA, they bind to specific palindromic sequences called restriction sites. Such palindromic DNA sequences or inverted repeats are commonly found in regions of functional significance, such as the origin of replication, gene operator sites, and regions containing transcription termination signals.
The host bacteria protect their own genomic DNA from these enzymes by methylating these sites. Some...