Abstract

Our 2018 iGEM project focuses on one the most ancient of Earth’s inhabitants: the horseshoe crab. The horseshoe crab is a type of chelicerate arthropod and there are several known species, three of the most popular being the Japanese horseshoe crab, the Singapore species, and the Atlantic horseshoe crab (Limulus polyphemus). The horseshoe crab is a particularly relevant species due to their characteristic blue hemolymph, which contains the copper-yielding hemocyanin protein that is responsible for oxygen transportation and delivery in their bodies. In addition to being used as bait by fisherman and playing an important role in our ecosystem -- they are eaten by sea turtles and their eggs provide a good food source for various shorebird species -- for the last 5 decades their blood has also been harvested for pharmaceutical purposes. The crabs are used to perform the Limulus amebocyte lysate (LAL) test, which is widely used for detection of bacterial endotoxins. The test relies on the horseshoe crab amebocytes’ ability to react with lipopolysaccharides (LPS), a component of negative-gram bacterial membranes, and while in contact initiate a protein cascade that ends with coagulation and cellular clotting to trap the bacteria. The amebocytes are able to do this because of the endotoxin-sensitive, intracellular, serine protease zymogen Limulus factor C. Factor C initiates the transduction pathway; in the presence of LPS, factor C selectively cleaves 103-Arg,104-Ser,105-Ile and 105-Ile to form Factor B. The active form of Factor B cleaves 98-Arg and 99-Ile in the horseshoe crab proclotting enzyme, thereby activating it.

All modern injectable medicines are required by the FDA to be tested for endotoxins and other harmful substances using LAL extracts from horseshoe crab blood. To prepare LAL, companies draw about one-third of an individual crab’s blood and release them back into the wild. Recent data shows that harvesting has contributed to an increase in the mortality rate of the species by as much as 30%, which not only poses a threat to their existence but also disrupts the ecological balance of the coast, affecting other species as well. We plan to create a recombinant limulus factor C in Pichia pastoris to minimize pharmaceuticals use of horseshoe crabs. We will do this by attaching a cellulose binding domain and GFP on a plasmid to...

Accumsan mus tortor nunc aliquet

Aliquam ut ex ut augue consectetur interdum. Donec amet imperdiet eleifend
fringilla tincidunt. Nullam dui leo Aenean mi ligula, rhoncus ullamcorper.