Question

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure?

(a) on the surface of the protein
(b) inside a cavity on the protein surface
(c) buried in the interior of the protein
(d) forms on the surface of the protein in the presence of ligand

Answer 1

The protein's ligand-binding site is typically located in a depression on the molecular surface, determined by the protein's tertiary structure, and it is most commonly inside a cavity on the protein surface. Therefore, correct option is b.

Step-by-step explanation:

Proteins bind selectively to small-molecule targets known as ligands. This selectivity is crucial for proteins to perform their diverse functions, such as carrying oxygen, as myoglobin does, or acting as enzymes facilitating biochemical reactions. The specific region where a protein interacts with a ligand is called the binding site.

The location of the binding site is generally a depression on the molecular surface of the protein, which is determined by the protein's tertiary structure.

Although there are various types of receptors, including internal receptors that bind hydrophobic ligands and have intracellular effects, and cell-surface receptors that bind hydrophilic ligands and can initiate signal transduction pathways, the ligand-binding site for the majority of these proteins is typically on the surface or in a cavity on the surface of the protein.

Thus, for the given options, the protein's ligand-binding site is most commonly located inside a cavity on the protein surface (b).