Question

It was thought that GPP130, a host membrane protein that cycles between the Golgi apparatus and endosomes, might assist STx in evading degradation and reaching the endoplasmic reticulum as it binds the toxin with a Kd of 25 mm. Prior research showed that exposure to manganese (Mn2+) degrades GPP130.

A novel compound was developed which occupies the site on STx where GPP130 binds the toxin. A drug with which value of Kd for binding to STx is most effective?
A. 0.25 mM
B. 2.5 mm
C. 25 mm
D. 250 mm

Answer 1

A drug with a lower Kd for STx binding would be more effective at blocking STx from interacting with GPP130. The best option from the choices is a Kd value of 0.25 mm, indicating the highest binding affinity and thus greatest efficacy in prevention of STx reaching the ER.

Step-by-step explanation:

The student is inquiring about a biochemical interaction between the shiga toxin (STx) and a protein called GPP130. GPP130 is a receptor that facilitates the movement of STx to the endoplasmic reticulum, thereby escaping degradation.

Manganese (Mn2+) exposure degrades GPP130, hindering this pathway. A novel compound that competes for the binding site on STx, preventing GPP130 binding, has been developed.

For therapeutic efficacy, this compound should ideally have a lower dissociation constant (Kd) than that of GPP130 for STx to successfully outcompete it and prevent the toxin's pathway to the ER.

The Kd value indicates the affinity between a ligand and its receptor, with a lower Kd reflecting a higher affinity. A drug with a Kd of 0.25 mm would be the most effective option provided as it has the highest affinity for STx compared to the other options.

This would effectively block STx from binding to GPP130 and promote its degradation, preventing the toxin from reaching the ER.