Early Nitrogenase Ancestors Encompassed Novel Active Site Diversity
Sarah L Schwartz1,2, Amanda K Garcia3, Betül Kaçar3
1Microbiology Graduate Program, Massachusetts Institute of Technology, Cambridge, MA.
Molecular Biology and Evolution
|October 19, 2022
Summary
Ancestral sequence reconstruction reveals that early nitrogenase ancestors had unique substrate channels not found today. This suggests ancient environmental pressures shaped enzyme specificity.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Bioinformatics
Background:
- Ancestral sequence reconstruction (ASR) predicts ancestral protein states, aiding in understanding protein family evolution.
- Nitrogenases are crucial enzymes involved in nitrogen fixation, with diverse extant forms.
Purpose of the Study:
- To compare inferred nitrogenase ancestors with extant sequences to understand evolutionary changes in substrate channels.
- To investigate the functional implications of ancestral protein states on enzyme specificity.
Main Methods:
- Utilized ancestral sequence reconstruction (ASR) to infer ancestral nitrogenase sequences.
- Compared inferred ancestral states of key substrate channel residues with extant nitrogenase sequence diversity.
- Analyzed the physiochemical properties of ancestral and extant substrate channel residues.
Main Results:
- Key substrate channel residues in inferred nitrogenase ancestors are absent in extant sequences.
- Ancestral substrate channel compositions are rarely found even in broader physiochemical contexts.
- This suggests significant divergence in substrate channel structure and potentially specificity over evolutionary time.
Conclusions:
- Earliest nitrogenase ancestors likely possessed distinct substrate channel compositions compared to modern enzymes.
- Environmental selection pressures in ancient settings may have driven nitrogenase substrate specificity.
- ASR is a valuable in silico tool for generating hypotheses about ancestral enzyme function and guiding experimental validation.
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