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A transition probability model for amino acid substitutions from blocks
Shalini Veerassamy1, Andrew Smith, Elisabeth R M Tillier
1Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
Summary
This study introduces a new protein evolution model, the Probability Matrix from Blocks (PMB). PMB approximates amino acid substitution probabilities using evolutionary distance, improving upon BLOSUM matrices for evolutionary analyses.
Area of Science:
- Bioinformatics
- Computational Biology
- Evolutionary Biology
Background:
- Substitution matrices like BLOSUM are vital for protein sequence alignment and comparison.
- BLOSUM matrices, derived from protein blocks, enhanced alignment accuracy over older PAM matrices.
- However, BLOSUM matrices lack an evolutionary model and cannot correct for multiple substitutions.
Purpose of the Study:
- To develop a novel evolutionary model for protein evolution.
- To approximate amino acid substitution probabilities as a function of evolutionary distance.
- To create a model compatible with existing BLOSUM matrices.
Main Methods:
- Utilized the Blocks database of protein alignments.
- Applied the principle of additivity of evolutionary distances.
- Approximated amino acid substitution probabilities based on actual evolutionary distance.
Main Results:
- Developed the Probability Matrix from Blocks (PMB) model.
- PMB defines a new evolutionary model for protein evolution.
- The PMB model is compatible with and derived from BLOSUM matrices.
Conclusions:
- The PMB model provides an evolutionary framework for protein sequence analysis.
- This model allows for the estimation of actual amino acid substitutions, correcting for multiple hits.
- The PMB model is easily implemented and enhances evolutionary analyses of protein sequences.