Question

Biochemistry

A researcher is trying to identify potential ligands for a protein, P. She determines the equilibrium dissociation constants (Kd) for 4 proposed ligands-L M, N, and O: P + L → PL Kd= 100 μM P +N → PLKd = 100 mM P + O → PL Kd = 100 nM Which of the proposed ligands binds the tightest to protein P? O M O N DQuestion 2 2 pts Sketch and label ligand binding curves for the binding of ligands L and M to protein P Upload Choose a File

need help on question 2. I'm not sure if question 1 plays a part in question 2 , thanks in advance!

Answer 1

Question 1 and 2 are inter-related in the sense that the former helps identify the ligand with higher affinity as a lesser affinity ligand gives a more linear ligand-binding curve when plotted versus concentration of the ligand.

1) The dissociation constant Kd for the reversible reaction P + L <-----> PL is given as Kd = ([P][L])/[PL]. Hence, with better binding ligands, the concentration of PL increases, leading to a lower Kd in terms of concentration. Thus, a better binding ligand gives a lower dissociation constant. This gives the affinity of ligands L, M, N and O in the order N < M < L < O giving O to be the ligand with the highest affinity.

2) Now between L and M, it is found that L has better affinity than M. From the lack of more concentration vs binding % data, only rough, relative curves can be given which are as given below:

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