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Function

VesB, a serene protease found in the bacterium Vibrio cholerae, plays an important role in pathogenesis and intestine growth. VesB’s function is cleaving A subunit of cholera toxin, which helps in the activation of itself. The protease’s substrate may consist of a protein with arginine (XXRXX) and the products (XXR+XX).

Disease

Cholera, caused by Vibrio cholerae, is an infectious intestinal disease well known for its severe symptoms of diarrhea and cramps, which often results in death. The first sign of whether or not an individual has contracted the disease is the quick onset of diarrhea increasing in intensity over time. Secondary symptoms include vomiting, extreme thirst, abdominal cramps, and a blue-gray coloring. Lastly, the blood would thicken due to loss of fluid.

Cholera toxin, a byproduct of Vibrio cholerae, decreases the amount of fluid in the intestines. The toxin is produced by the CTXf bacteriophage residing subunit. The A subunit consists of an A1 domain containing the enzymatic active site and it assembles into a pentameric ring surrounding a central pore.

Relevance

Cholera has been recorded in early Sanskrit writings and has been a prevalent disease on the Indian subcontinent for years. In the 19th century, cholera spread across Europe and eventually advanced to North and South America. Today it continues to be a serious health issue in Africa, Asia, and Latin America.

There are as many as 200,000-500,000 cases per year and the mortality rates can reach as high as 20-50%. There are currently no effective prophylactics and treatment by rehydration often does not work because of the lack of clean water supplies. Research currently aims at targeting the cholera toxin itself, focusing specifically on the inhibition of its binding to receptors in the intestine and the development of anti-secretory agents.

Structural highlights

This structure is a quaternary structure and the primary in VesB is beta sheets. In the molecule it has an alpha helix and some random coils spread around in the structure. VesB is made up of two different domains, it can be shown in this view. VesB has has two in it domains. The two different type of domains are the N-terminal and C-terminal domain. This molecule is and does not react well with water. The hydrophobic are important because they show the area where the active site is located it is labeled in purple. Being hydrophilic shows that it does mix well with water. They are both shown throughout the molecule. The of the molecule is made up of 3 amino acids. The amino acids are Asp125-His78-Ser221 which are highlighted in red, blue, and green. The other amino acids that are found in the active site are highlighted black. It has a hydrophobic pocket that is made up of Val159, Val180, Ile164 and has a cleavage site made up of two amino acids Arg32, Ile33.

Kinetic Data

VesB activity was measured with different concentrations of Boc-Gln-Ala-Arg-7-amino-4-AMC in 5 mM HEPES, pH 7.5, at 37 °C. B, purified VesB (0.08 g/ml) was incubated with 50M leupeptin, 1 mM benzamidine, or 10 mM EDTA for 10 min at 37 °C. The Boc-Gln-AlaArg-7-amino-4-AMC (0.05 mM final concentration) was added and VesB activity was measured. When Boc-Gln-AlaArg-7-amino-4-AMC increases so does the pmol/min. ^[1][2][3][4]