Question

Calmodulin has low affinity for _____________

(a) magnesium ions

(b) iodine

(c) non-stimulated cells

(d) stimulated cells

The question was posed to me in a job interview.

Enquiry is from Cell Signaling and Signal Transduction in section Cell Signaling and Signal Transduction of Cell Biology

Answer 1

The correct choice is (c) non-stimulated cells

For explanation: Calmodulin contains 4 binding sites for calcium. It does not have sufficient affinity for Ca^2+ ions in non-stimulated cells. When the calcium ions concentration increases in response to a stimulus, the ions bind to calmodulin, changing its conformation.