# Recombinant human enamelin produced in Escherichia coli promotes mineralization in vitro

## TL;DR

Scientists produced a human enamel protein in bacteria, which can help form mineralized structures in the lab.

## Contribution

A scalable microbial method to produce recombinant human enamelin is developed.

## Key findings

- Recombinant human enamelin was successfully expressed in Escherichia coli with a yield of ~10 mg per liter.
- The protein promoted calcium phosphate mineralization at 0.5 mg/ml in vitro.
- The method uses Ni2+ and 30 mM imidazole for optimal purification.

## Abstract

Enamelin is an enamel matrix protein that plays an essential role in the formation of enamel, the most mineralized tissue in the human body. Previous studies using animal models and proteins from natural sources point to a key role of enamelin in promoting mineralization events during enamel formation. However, natural sources of enamelin are scarce and with the current study we therefore aimed to establish a simple microbial production method for recombinant human enamelin to support its use as a mineralization agent.

In the study the 32 kDa fragment of human enamelin was successfully expressed in Escherichia coli and could be obtained using immobilized metal ion affinity chromatography purification (IMAC), dialysis, and lyophilization. This workflow resulted in a yield of approximately 10 mg enamelin per liter culture. Optimal conditions for IMAC purification were obtained using Ni2+ as the metal ion, and when including 30 mM imidazole during binding and washing steps. Furthermore, in vitro mineralization assays demonstrated that the recombinant enamelin could promote calcium phosphate mineralization at a concentration of 0.5 mg/ml.

These findings address the scarcity of enamelin by facilitating its accessibility for further investigations into the mechanism of enamel formation and open new avenues for developing enamel-inspired mineralized biomaterials.

The online version contains supplementary material available at 10.1186/s12896-024-00875-0.