In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

[Q]:  Members of the steroid / hormone nuclear receptor superfamily regulate target gene transcription via recognition and association with specific cis - acting sequences of DNA , called hormone response elements ( HREs ) .
[A]: nuclear receptor superfamily


[Q]:  To further identify the residues responsible for the activity , we isolated the mutant viruses that were not neutralized with the soluble form of MHV receptor proteins , since such mutants were expected to have mutations in amino acids responsible for receptor - binding activity .
[A]: MHV receptor proteins


[Q]:  We identified two potential phosphorylation sites at serine49 and serine133 , both of which seem to be necessary for Myf - 5 activity .
[A]:
Myf - 5