Many silicatein mutants together make better nanoceria
Evolving silicatein for ceria biomineralization never yielded one champion sequence; mixed truncated mutants and intact catalytic-triad knockouts still mineralize, implying synergistic mosaicism.
Source
Directed Evolution of Silicatein Reveals Biomineralization Synergism between Protein Sequences
What they did
Authors fused silicatein to trigger factor, built error-prone libraries, screened E. coli survival-linked mineralisation, and compared in-vitro nanoceria from WT versus mutants by TEM and catalytic-triad alanine mutants.
What they found
Mutant 2.6 made 3.37 nm particles versus 2.46 nm for WT; H165A/S26A still mineralized similarly to WT; sponge silicateins share only 54–73% identity. Truncations of ~171 aa remained functional.
The limits
What it doesn't show
This is not a process-optimised, kilogram-scale green manufacture of ceria, nor proof that mosaicism is how sponges mineralize in vivo.
Key terms
- Silicatein
- Sponge biomineralization enzyme originally making silica spicules; here used for ceria.
- Nanoceria
- Cerium oxide nanoparticles formed from a CAN precursor under mild aqueous conditions.
- Catalytic triad
- Ser/His (and related) residues whose knockout still left mineralisation activity.
- Genetic mosaicism
- Several mutant sequences coexisting rather than a single optimized gene.
- Trigger factor fusion
- Solubility tag used to express recombinant silicatein.
Flashcards
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The mineralized product here is:
Common questions
Did one super-silicatein win?
No—several mutants/mosaics enhanced activity.
Did triad knockouts kill activity?
No significant drop versus WT in nanoceria recovery.
Particle size for mutant 2.6 vs WT?
3.37 ± 0.15 nm vs 2.46 ± 0.17 nm.
In-vitro mineralisation mix?
2 μM protein, 2 mM CAN, pH 7 Tris, room temperature.
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