Review Question - QID 107981

An 8-year-old boy presents to his primary care pediatrician for routine check-up. During the visit, his mom says that she has noticed yellow bumps on his eyelids and was concerned about whether they were a problem. Upon hearing this concern, the physician inquires about parental health studies and learns that both parents have high cholesterol despite adhering to a statin regimen. Furthermore, other family members have suffered early myocardial infarctions in their 30s. Physical exam reveals flat yellow patches on the patient's eyelids bilaterally as well as hard yellow bumps around the patient's ankles. Based on clinical suspicion an LDL level is obtained and shows a level of 300 mg/dL. What protein is most likely defective in this patient causing these findings?