What is the name of the enzyme that “reads” the DNA and “writes down” (transcribes) the code into messenger RNA (mRNA)?

You are studying a protein that you call protein x. there is an aspartic acid at a key position in protein x which is important in the folding and stabilization of that protein. if this aspartic acid is changed to a different amino acid, which type of amino acid substitutions is most likely to allow the protein to fold normally?