Team:Concordia/Scaffold

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  • Lactococcus Lactis
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The Scaffold

Extracellular scaffolds are known to occur naturally in eukaryotic and prokaryotic organisms alike, although their function differs greatly depending on the type of organism that expresses them and, of course, on the enzymatic conformation of the scaffold.

Some types of extracellular scaffolds or matrices are currently being studied in many different fields. Their uses range from their direct application in tissue engineering for wound healing (1), to drug delivery for the treatment of cancer (2) and to aid in the production of biofuels (3), to mention a few examples.

For our work, we focused on the naturally occurring scaffold produced by the bacterium Clostridium thermocellum. This organism displays a remarkably large extracellular cellulase system known as the cellulosome, which is used by the organism for the degradation of cellulose to produce ethanol. The cellulosome of this particular organism consists of nearly 20 different catalytic subunits of weights ranging in size from about 40 to 180 kDa and it is an extremely complex protein system (4).

The cellulosome is of interest to us due its structure and conformation; the different catalytic portions of this protein complex are ordered so that they may carry out a sequential pathway of degradation. We wish to take advantage of this ordered sequencing for our own scaffold.

Cohesins and Dockerins

The way the scaffold orders the proteins in such a tight and efficient way depends entirely on its fundamental conformation and can be manipulated to yield a useful final product for humans.

One of the types of protein products made by C. thermocellum are known as cohesins. The cohesins form part of the fundamental structure of the scaffold. They act as docking bays to potentially harbor the different proteins of interest that the scaffold would be designed to display.

The dockerins, on the other hand, are the complementary parts of the cohesins. They act as adaptors for the enzymes of interest and allow them to be attached to the scaffold by binding to their complementary cohesins on the scaffold. There exist different types of cohesins with their complementary types of dockerins, which allow us to assign sequential steps in a pathway with the certitude that the order of such reactions will be respected.

References

1	Brown, B., Lindberg, K., Reing, J., Stolz, D. B., & Badylak, S. F. (2006). The basement membrane component of biologic scaffolds derived from extracellular matrix. Tissue engineering, 12(3), 519-526
2	Mintz, C. S., & Crea, R. (2013). Protein Scaffolds. BioProcess International,11, 40-48
3	3. Kim, S., & Hahn, J. S. (2014). Synthetic scaffold based on a cohesin–dockerin interaction for improved production of 2, 3-butanediol in Saccharomyces cerevisiae. Journal of biotechnology, 192, 192-196
4	Wieczorek, A. S. (2012). Engineering Lactococcus lactis for the scaffold protein-mediated surface display of recombinant enzymes(Doctoral dissertation, Concordia University)