“Liquid-like” biomineralization protein assemblies: a key to the regulation of non-classical nucleation
Over the past several decades, numerous studies have attempted to define the general role that proteins play in the nucleation of biominerals in organisms. Recently, with the emergence of the non-classical nucleation scheme involving pre-nucleation cluster formation, amorphous mineral cluster assembly, and maturation/stabilization scenarios, there is a growing realization that proteins could efficiently regulate many steps in this process, resulting in precise control over the development of biogenic crystals or the indefinite stabilization of amorphous mineral phases in a wide variety of organisms. In this Highlight, we present a generic scheme where nucleation-specific biomineralization proteins containing intrinsically disordered and aggregation-prone sequences assemble to form a liquid- or fluid-like phase similar to that formed in the polymer-induced liquid phase (PILP) and in vitro liquid protein systems. This assembled protein phase is compatible with the physical-chemical properties of prenucleation clusters and amorphous mineral clusters, and can provide an environment for subsequent stabilization and/or transformation of the mineral phase under appropriate conditions and locations. We foresee some important applications arising from Nature's use of protein assemblies to create, stabilize, and transform amorphous mineral precursor phases.