Linear and inverted repetitions in protein sequences.

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Science

Background:

• Amino acid sequences form the basis of protein structure and function.
• Understanding internal regularities in protein sequences can provide insights into evolutionary processes.

Purpose of the Study:

• To investigate internal regularities within amino acid sequences of proteins.
• To explore the potential evolutionary mechanisms behind observed sequence patterns.

Main Methods:

• Utilized the genetic code to analyze amino acid sequences.
• Employed relative frequencies of amino acid alternatives in homologous proteins.
• Searched for linear and inverted repetitions in protein sequences.

Main Results:

• Both genetic code analysis and amino acid frequency methods yielded similar results.
• Identified significant linear and inverted repetitions in several protein sequences.
• These findings strongly suggest the presence of internal regularities.

Conclusions:

• A hypothesis for the origin of internal protein regularities was developed.
• The hypothesis posits a gene duplication model involving an ancestral loop.
• Symmetrical amino acid arrangements in ancestral loops may facilitate stabilization via side-chain interactions.