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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Atomic resolution density maps reveal secondary structure dependent differences in electronic distribution.

Paula I Lario¹, Alice Vrielink

¹Department of Molecular, Cellular and Developmental Biology, Sinsheimer Laboratory, University of California Santa Cruz, Santa Cruz, CA 95064, USA.

Journal of the American Chemical Society

|October 16, 2003

Summary

High-resolution X-ray crystallography of cholesterol oxidase reveals distinct electronic properties of peptide carbonyl groups in alpha-helices and beta-sheets. These findings offer new insights into enzyme electronic effects.

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Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures

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Area of Science:

Biochemistry
Structural Biology
Enzymology

Background:

Flavoenzymes play crucial roles in biological redox reactions.
Cholesterol oxidase (SCOA) is a 55kDa flavoenzyme involved in cholesterol metabolism.
Spectroscopic methods suggest peptide carbonyl groups in alpha-helices exhibit polarization.

Purpose of the Study:

To determine the X-ray crystal structure of SCOA at sub-Angstrom resolution.
To investigate the electronic characteristics of peptide carbonyl groups within alpha-helices and beta-sheets.
To correlate electronic differences with structural parameters in proteins.

Main Methods:

X-ray crystal structure determination of SCOA to 0.95 Å resolution.
Analysis of sub-Angstrom electron density maps.
Comparison of carbonyl group electronic density in alpha-helices and beta-sheets.

Main Results:

Observed increased polarization of main chain carbonyl electron density towards oxygen in alpha-helices.
Found greater charge density between carbon and oxygen in beta-sheet carbonyl groups.
Electronic differences were not correlated with peptide bond distance or planarity.

Conclusions:

Provides experimental evidence for electronic effects of alpha-helix dipoles in enzymes.
Highlights distinct electronic carbonyl group behaviors in different secondary structures.
Offers novel, experimentally based structural insights into enzyme electronic properties.