Question

Calmodulin is A. a nonspecific kinase. B. a protein that binds \(\mathrm{Ca}^{2+}\). C. a second messenger. D. an activator of nitric oxide synthase. E. a protein channel that facilitates the influx of \(\mathrm{Ca}^{2+}\).

Short answer

Answer: The primary function of Calmodulin is to bind with \(\mathrm{Ca}^{2+}\) ions, allowing it to play an essential role in regulating various cellular processes.

Step-by-step solution

Option A: a nonspecific kinase

Calmodulin is not a nonspecific kinase. A kinase is an enzyme that modifies other proteins by adding phosphate groups to them, but Calmodulin doesn't have this function.

Option B: a protein that binds \(\mathrm{Ca}^{2+}\)

Calmodulin is a calcium-binding protein that plays an essential role in several cellular processes. It can bind to and regulate the function of various target proteins in response to changes in calcium levels.

Option C: a second messenger

Second messengers are small molecules or ions that relay signals from receptors on the cell surface to target molecules inside the cell. Calmodulin is not a second messenger but rather a protein that binds to them to regulate cellular processes.

Option D: an activator of nitric oxide synthase

Nitric oxide synthase (NOS) is an enzyme that produces nitric oxide, a molecule involved in several physiological processes. Calmodulin can bind to NOS and regulate its activity. However, defining Calmodulin solely as an activator of NOS would be too narrow.

Option E: a protein channel that facilitates the influx of \(\mathrm{Ca}^{2+}\)

Calmodulin does not form a protein channel. Instead, it's a calcium-binding protein that can modulate the activity of other proteins in response to changes in calcium concentration. Based on the analysis, the correct answer is: B. a protein that binds \(\mathrm{Ca}^{2+}\).