Structure-based analysis of Bacilli and plasmid dihydrofolate reductase evolution.

Area of Science:

• Biochemistry
• Structural Biology
• Evolutionary Biology

Background:

• Dihydrofolate reductase (DHFR) is crucial for tetrahydrofolate-dependent biosynthesis.
• DHFR is a validated therapeutic target for infections and cancers.
• Understanding DHFR evolution aids in drug development and understanding microbial adaptation.

Purpose of the Study:

• To perform a structure-based computational analysis of bacterial and plasmid DHFR evolution.
• To compare the conservation patterns of active site and non-active site residues in chromosomal and plasmid DHFR.
• To investigate evidence of horizontal gene transfer in DHFR evolution.

Main Methods:

• Generated structure-based sequence alignments using 7 DHFR x-ray crystal structures and 350 homology models.
• Analyzed conservation of amino acid residues, secondary structure, and residue classes at active and non-active sites.
• Constructed DHFR-specific phylogenetic trees to identify evolutionary patterns.

Main Results:

• Active site positions in both plasmid and chromosomal DHFR are significantly more conserved than non-active site positions.
• Plasmid-encoded DHFR exhibits greater sequence and residue class conservation than chromosomal DHFR.
• Phylogenetic analysis revealed evidence of horizontal gene transfer in DHFR evolution.

Conclusions:

• Plasmid DHFR is under stronger evolutionary constraint, particularly in functionally important regions.
• The findings highlight the role of horizontal gene transfer in the dissemination and evolution of DHFR.
• This research provides insights into DHFR's evolutionary trajectory and potential for therapeutic targeting.