Comparative structural analysis of IS21 transposition complexes using Cryo-EM and AlphaFold3.

Area of Science:

• Genomics
• Structural Biology
• Computational Biology

Background:

• Transposition is a key mechanism in genome evolution, influencing gene expression and the spread of resistance.
• The IS21 transposon, encoding IstA and IstB, is a mobile genetic element critical for DNA transposition.
• Understanding transposon structure and dynamics is vital for comprehending genome plasticity.

Purpose of the Study:

• To compare cryo-electron microscopy (cryo-EM) structures of the IS21 transpososome with models generated by AlphaFold3 (AF3).
• To evaluate the capabilities of AF3 in predicting complex protein-DNA assemblies involved in transposition.
• To assess AF3's accuracy in modeling conformational changes and higher-order interactions within the transpososome.

Main Methods:

• Determined cryo-EM structures of the IS21 transpososome in pre- and post-transposition states.
• Utilized the public AlphaFold3 server to generate structural models of the transposon components.
• Performed a comparative analysis between experimental cryo-EM structures and AF3-predicted models.

Main Results:

• AF3 accurately predicts individual monomeric domains and some oligomeric arrangements within the IS21 transpososome.
• AF3 demonstrates limitations in capturing complex multi-protein/DNA assemblies.
• The prediction engine struggles with modeling conformational dynamics and higher-order interactions essential for transposition.

Conclusions:

• AF3 shows promise for predicting simpler protein structures but requires further development for complex biological assemblies like transpososomes.
• Experimental methods like cryo-EM remain indispensable for elucidating the intricate structures and dynamics of mobile genetic elements.
• The study highlights the current limitations of AI in fully replicating the complexity of biological molecular machinery.