Problem

Myocardial infarction, also known as a heart attack, occurs when blood flow stops or is restricted to a part of the heart. This damages the heart muscle and results in pain, discomfort, and/or shortness of breath. In the event of a myocardial infarction, ischemic injury to cardiac tissue releases key enzymes into the peripheral blood stream. Detection of these enzymes often assists in the diagnosis of infarction earlier on to determine treatment and improve a patient’s long-term outcome.
A cardiologist is interested in studying how quickly cardiac enzymes appear in the bloodstream following ischemic injury. She induces ischemic cardiac injury to several wild-type mice using coronary artery ligature to limit perfusion to cardiac tissue. Following this process, she draws blood samples from the mice at different time points and isolates proteins known to be released after ischemic injury. The protein levels over the course of the experiment are shown in Figure 1.
Figure 1. Appearance of cardiac enzymes following ischemic injury versus concentration. The dotted-line represents the minimal threshold for clinical detection in a sample of peripherally obtained blood.
Which protein in cardiac muscle is most directly related to the function of tropomyosin
Please choose from one of the following options.