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Combining X-Ray Crystallography with Small Angle X-Ray Scattering to Model Unstructured Regions of Nsa1 from S. Cerevisiae
Published on: January 10, 2018
Crystal structure of yeast Sco1
Carnie Abajian1, Amy C Rosenzweig
1Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
Summary
Sco proteins are crucial for assembling the copper A site in cytochrome c oxidase (COX). Researchers determined the crystal structure of yeast Sco1, revealing a novel copper-binding site and insights into its function in aerobic respiration.
Area of Science:
- Biochemistry
- Structural Biology
- Cellular Respiration
Background:
- Sco proteins are essential for the assembly of the dinuclear copper A site in cytochrome c oxidase (COX).
- These proteins feature a conserved CXXXC motif for copper binding and potential thiol:disulfide oxidoreductase activity.
- Cytochrome c oxidase is the terminal enzyme in aerobic respiration.
Purpose of the Study:
- To determine the high-resolution crystal structures of Saccharomyces cerevisiae apo Sco1 (apo-ySco1) and copper-bound Sco1 (Cu-ySco1).
- To elucidate the copper-binding mechanisms and functional roles of Sco proteins in eukaryotes.
- To provide structural insights into the interactions between Sco1 and its partner proteins.
Main Methods:
- X-ray crystallography was used to determine the structures of apo-ySco1 and Cu-ySco1 to 1.8- and 2.3-Å resolutions, respectively.
- Copper ions were introduced by soaking apo-ySco1 crystals.
- Structural analysis focused on identifying copper-binding sites, conserved motifs, and flexible regions.
Main Results:
- Yeast Sco1 adopts a thioredoxin-like fold, consistent with homologs from other species.
- An unexpected copper-binding site was identified involving Cys181 and Cys216 in yeast Sco1.
- The conserved CXXXC cysteines (Cys148 and Cys152) demonstrated potential for redox chemistry.
- A flexible loop (Sco loop) containing an essential histidine (His239) was observed to interact with cysteine residues.
- Complementary electrostatic surfaces suggest interaction sites with yeast Cox17 and COX2.
Conclusions:
- The high-resolution structure of yeast Sco1 provides novel insights into eukaryotic Sco protein structure and copper binding.
- The identified unexpected copper-binding site expands our understanding of Sco protein function.
- Structural data supports the role of Sco proteins in copper ion delivery and redox processes essential for COX assembly and aerobic respiration.
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