Adrenocorticotropic hormone $($ACTH$)$ is derived from a precursor called

proopiomelanocortin $($POMC$),$ which is processed to form the active $39-$

amino acid peptide ACTH. Mutations in the amino acids at positions $15-18$

are crucial for ACTH's binding to its receptor. A patient with low cortisol

levels has a defective ACTH function due to a mutation. We must identify

which specific mutation at these critical positions is responsible for the low

cortisol levels. $($Three Correct answers for this question$)$

A$.$ Lys$-$Ala$-$Arg$-$Arg $($aa$15-$aa$18)$

B$.$ Lys$-$Arg$-$Lys$-$Arg

C$.$ Lys$-$Ala$-$Arg$-$Ala

D$.$ Lys$-$Lys$-$Arg$-$Arg