Review Question - QID 109660

An 11-year-old male is brought in by ambulance to the emergency department after being a restrained passenger in a motor vehicle accident. His father was driving him to soccer practice when they were hit by a wrong way driver. On presentation, his temperature is 101°F (38.3°C), blood pressure is 100/62 mmHg, pulse is 108/min, and respirations are 21/min. He is found to be agitated and complains of nausea, severe epigastric pain, and lower extremity pain. Physical exam reveals lacerations and ecchymosis on his left forehead, right flank, and lower extremities. Radiographs demonstrate an open book fracture of the pelvis as well as bilateral femur fractures. Despite multiple interventions, his condition deteriorates and he passes away from his injuries. Post-mortem pathologic examination of abdominal tissues reveals white deposits containing calcium. Abnormal activity of which of the following proteins is most likely responsible for these deposits?