Abstract

Background: A lipid bilayer membrane commonly encloses specialised compartments where biological mineral formation (biomineralization) takes place. The function of membranes in the biomineralization process is currently poorly understood.

Results: We discovered Silicanin-1 (Sin1) as a conserved diatom membrane protein found in silica deposition vesicles (SDVs) of Thalassiosira pseudonana while researching the biomineralization of SiO2 (silica) in diatoms. For the first time, silica synthesis in vivo may be followed by fluorescent microscopy of GFP-tagged Sin1, which is a biomineralization protein. The investigation showed that the interaction of the N-terminal domain of Sin1 with the organic matrix within the SDVs resulted in integration of Sin1 into the biosilica. Via a synergistic interaction with long-chain polyamines, in vitro tests revealed that the recombinant Sin1 N-terminal domain undergoes pH-triggered assembly into sizable clusters and encourages silica formation.

Conclusions: Sin1 is the first SDV transmembrane protein to be discovered, and because it is highly conserved throughout the diatom kingdom, it may play a crucial part in the biomineralization of diatom silica. Sin1 might act as a molecular link via which the SDV membrane regulates the formation of organic matrices that create biosilica in the SDV lumen through interactions with long-chain polyamines.