When one plus one equals three: biochemistry and bioinformatics combine to answer complex questions

Area of Science:

• Evolutionary biology
• Molecular biology
• Biochemistry

Background:

• Ortholog analyses are crucial for understanding gene function across species.
• However, sequence similarity (orthology) does not guarantee functional conservation.
• The Survival Motor Neuron (SMN)-complex is essential for spliceosomal UsnRNPs assembly.

Purpose of the Study:

• To investigate the evolutionary trajectory and functional relevance of SMN-complex components.
• To assess the utility of combining bioinformatic and biochemical methods for studying macromolecular complexes.

Main Methods:

• Comparative genomics and bioinformatic analyses of orthologs.
• Biochemical characterization of the Drosophila SMN-complex.
• Sequence divergence analysis to infer evolutionary pressures.

Main Results:

• Many SMN-complex components have ancient evolutionary origins.
• Two predicted orthologs were absent in the biochemically purified Drosophila SMN-complex.
• Despite the absence of these predicted orthologs, the Drosophila SMN-complex remained functional.
• Bioinformatic re-assessment indicated rapid sequence divergence for the missing orthologs in Drosophila.

Conclusions:

• Orthology is insufficient for predicting functional roles in complex molecular machinery.
• Integrated bioinformatic and biochemical approaches are essential for accurate functional assessment of proteins within complexes.
• Evolutionary pressures can lead to the loss of predicted orthologs without compromising essential complex functions.