The role of phosphorylation and dephosphorylation of shell matrix proteins in shell formation: anin vivoandin vitrostudy

Jinzhe Du,Guangrui Xu,Chuang Liu,Rongqing Zhang

doi:10.1039/c8ce00755a

Abstract

Phosphorylation of shell matrix proteins is critical for shell formationin vivoand can modulate calcium carbonate formationin vitro.

Highlights

Protein phosphorylation is a fundamental mechanism regulating many aspects of cellular processes
The extrapallial fluid has been demonstrated to contain matrix proteins that play important roles in the formation of shells.[36]. It can facilitate the formation of a multilevel layered nacre-like structure on the pearl nucleus.[37]. The diagram of this experiment is shown in Fig. S2.† After injection, the phosphorylation of extrapallial fluid proteins by enzyme linked immunosorbent assay (ELISA) was detected, and the phosphorylation level of anti-phosphoserine/threonine/tyrosine injection oysters was reduced significantly by nearly 45% after 3 days and by 87% after 6 days (Fig. S3A†)
In the antiphosphoserine/threonine/tyrosine injected group, compared with the control group (Fig. 1A–D), the morphology of the prismatic layer was not disturbed and showed a normal prism structure after antibody injection for 3 days (Fig. 1E and F), while after 6 days, the boundaries of prisms became unclear and some holes appeared within the prisms (Fig. 1G and H) and the growth of the prismatic layer was greatly disturbed

Summary

Introduction

Protein phosphorylation is a fundamental mechanism regulating many aspects of cellular processes. Shell matrix proteins (SMPs) control the crystal nucleation, polymorphism, morphology, and organization of calcium carbonate crystallites during shell formation. The ability of SMPs to inhibit calcium carbonate formation has been reduced. Borbas et al showed that a phosphorylated shell matrix was more effective in inhibiting crystal growth than a dephosphorylated matrix.[23] Interestingly, one third of the Ser/Thr phosphorylated sites with family with sequence similarity 20C (Fam20C) recognition site Ser-x-Glu were found in the Lottia gigantea shell matrix proteome,[24] indicating their potential function in biomineralization. We have shown that knockdown of Fam20C, which can phosphorylate biomineralization related proteins in vivo, resulted in abnormal stacking of calcium carbonate crystals at the edges of nacre tablets.[25] These results suggest that phosphorylation is important in shell formation

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Conclusion