The octameric histone core of the nucleosome. Structural issues resolved

Area of Science:

• Structural Biology
• Crystallography
• Molecular Biology

Background:

• The histone octamer is a fundamental component of chromatin structure.
• Previous low-resolution studies and initial high-resolution attempts yielded conflicting data on its precise dimensions.

Purpose of the Study:

• To accurately determine the crystal structure of the histone octamer at high resolution.
• To resolve discrepancies in reported histone octamer dimensions and reconcile conflicting structural data.

Main Methods:

• X-ray crystallography at 3.1 A resolution.
• Refinement of crystallographic data using identical experimental intensity data as previous studies.
• Re-evaluation and precise determination of heavy-atom site location.

Main Results:

• The histone octamer's crystal structure was determined with a refined R value of 25.5%.
• The overall shape and dimensions of the histone octamer are significantly different from the initially reported model.
• The new dimensions align with previous low-resolution observations.

Conclusions:

• A small shift in heavy-atom site determination led to a misinterpretation of the histone octamer's structure in prior analyses.
• The revised crystal structure provides an accurate representation of the histone octamer's size and shape.
• This study clarifies the structural characteristics of the histone octamer, resolving previous analytical conflicts.