Repeated folding pattern in copper-zinc superoxide dismutase

Area of Science:

• Biochemistry
• Structural Biology
• Protein Science

Background:

• Globular proteins can possess internal repeated structural motifs.
• Many enzymes exhibit a pseudo-symmetric, two-lobed architecture with approximate 2-fold symmetry.
• This motif can also occur within a single protein domain, forming two interlocked, topologically similar subdomains.

Purpose of the Study:

• To investigate the presence and significance of repeated folding patterns in protein domains.
• To analyze the structural organization of copper-zinc superoxide dismutase.
• To discuss the evolutionary implications of tandem gene duplication in forming paired protein structures.

Main Methods:

• Structural analysis of globular proteins.
• Identification of pseudo-symmetric architectures and repeated motifs.
• Superimposition of equivalent alpha-carbon atoms to quantify structural similarity (RMSD of 1-2 A).

Main Results:

• Copper-zinc superoxide dismutase was found to contain two paired subdomains.
• These subdomains exhibit significant structural similarity, suggesting a common evolutionary origin.
• The paired subdomains interlock symmetrically, forming a compact globule essential for domain integrity.

Conclusions:

• The repeated folding pattern is a significant feature in protein structure, exemplified by copper-zinc superoxide dismutase.
• Paired structures likely evolved from dimeric precursors via tandem gene duplication.
• The interdependency of subdomains suggests they function as a unit, not as independent folding entities.