Dr. Stewart Loh
Dr. Loh’s research group uses the tools of protein engineering and folding to convert existing proteins into molecular switches for use in biotechnology and medicine. They have recently developed the Domain-Swapping Module (DSM) technology for creating self-assembling, ‘smart’ biomaterials. DSMs are small proteins that can be tagged onto target proteins of choice in order to cause the targets to self-assemble into extensive proteinaceous networks including hydrogels. The distinctions between DSM technology and others are that DSM-assembled materials: (1) possess the biological functions of the target proteins, (2) can self-assemble in response to a variety of stimuli, and (3) are fully genetically encoded.
The DSM consists of a ‘lever’ protein inserted into an ‘assembler’ protein. The lever forces the assembler apart at the site of insertion, causing the latter to unfold. The assembler protein then refolds with other assemblers by a mechanism known as domain swapping. The result is a three-dimensional meshwork in which the nodes are domain-swapped assemblers.
As proof-of-concept, we fused a small DSM to green fluorescent protein (GFP). An additional benefit of the technology is that large quantities of the recombinant protein can be produced inexpensively by bacteria. One gram of pure protein was obtained from two liters of E. coli. Figure 2 shows that the DSM-tagged GFP self-assembles into a hydrogel. The hydrogel fluoresces green, indicating that the function of GFP is retained in the final material.