Evolutionary processes and evolutionary noise at the molecular level. II. A selectionist model for random fixations...

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• Protein molecules function as compromises due to competing functional demands at different sites.
• Existing models often view proteins as suboptimal, with some functions optimized at the expense of others.

Purpose of the Study:

• To propose a model where protein selection coefficients can be broken down into partial coefficients for individual functions.
• To explain how proteins maintain adaptation through kaleidoscopic changes at variable sites.
• To provide a theoretical basis for a molecular evolutionary clock.

Main Methods:

• Decomposition of selection coefficients into partial coefficients for protein functions.
• Analysis of a selective mechanism promoting primary structure changes at variable sites.
• Integration of internal environmental changes into a constant-environmental selection model.

Main Results:

• Proteins fluctuate around maximal adaptation, with selection acting on individual functions.
• A model is presented where selection occurs without genetic load, leading to multipolymorphism.
• The model provides a theoretical foundation for a molecular evolutionary clock, dependent on functional density.

Conclusions:

• Genetic sufficiency is a more adequate concept than genetic optimality for biological fitness.
• Observed substitution frequencies reflect resistance hierarchies, not just randomness.
• Evolutionary significant substitutions can be identified by monitoring functional density changes.