Simple mechanisms for the evolution of protein complexity.

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• Proteins exhibit complex structures and functions, including folding, complex assembly, and allostery.
• Traditionally, protein evolution was believed to occur through gradual changes driven by natural selection over long periods.

Purpose of the Study:

• To investigate the mechanisms underlying the evolution of protein complexity.
• To challenge the classical view of gradual evolutionary trajectories for protein features.

Main Methods:

• Review of evidence from biochemistry, protein engineering, and molecular evolution studies.
• Analysis of the genetic and physical underpinnings of protein multimerization, allostery, and novel folds.

Main Results:

• Naturally occurring proteins often possess latent complex properties, accessible via few mutations.
• Underlying physical properties for complex features can be fortuitous by-products of simpler protein architectures.
• Vast sequence spaces encode complex protein features, allowing access from numerous evolutionary starting points.

Conclusions:

• Protein complexity can evolve rapidly through sudden transitions, not just gradual change.
• Both random chance and natural selection are critical drivers of protein molecular evolution.
• The evolution of complex protein functions is facilitated by short and numerous mutational pathways.