hello everyone I have a candidate gene. I know the amino acid sequence of the protein it is converted into by querying the transcript of this gene, and I predict the tertiary structure of the protein by its amino acid sequence

I have some questions now:

1. How to determine the receptor of this protein (from gene transcription)?
2. How to mark the ligand position?
3. How to mark the position of the mark on the protein on the base sequence of the corresponding gene?

Any help will be appreciated