Sandbox Reserved 492: Difference between revisions

The [http://en.wikipedia.org/wiki/Crystal_structure crystal structure] of the purified form of ''' Cholix Toxin''' or '''CT''' was determined in 1995. [3] It is an oligomeric bacterial protein found to be made up of six individual subunits. V. cholerae toxin, along with other similar bacterial enterotoxins seem to share an evolutionary conserved <scene name='Sandbox_Reserved_496/Secondary_structure/1'> secondary structure </scene> composition comprising of about 13 alpha-helices and 10-12 Beta-sheets. The protein is then further divided into one single A-subunit and 5 individual B- subunits.The A-subunit makes up what is known as the enzymatic portion of the protein while the 5 copies of the B-subunit are responsible for the binding to the ligand receptor. The toxin binds highly specifically and tightly to a [http://en.wikipedia.org/wiki/GM1_gangliosidoses GM1 gangliosides] on the surface of the host's cells. In this X-Ray Diffraction image we can see the <scene name='Sandbox_Reserved_496/Binding_site/1'>catalytic</scene> site, which in this case has been complexed with an allosteric inhibitor (red and yellow space filling atoms). Recent studies have indicated several amino acid <scene name='Sandbox_Reserved_496/Critical_amino_acids/2'> residues </scene> located proximally to the active site which are critical for enzymatic activity. Specifically, site directed mutagenesis indicated that when altered, the mutation results in a termination of the proteins toxicity, rendering it essentially harmless.