This chapter outlines methods to purify soluble adenylyl cyclase (AC7) expressed in an Escherichia coli (E. coli) heterologous expression system. Guidelines are provided for constructing the expression plasmids, optimizing expression, culturing, and purifying the proteins. Purification requires two chromatographic steps. A histidine tag (H6) is incorporated into the expression vector and utilized for affinity purification on a Ni-NTA column. Subsequently, an anion exchange column is employed to further purify the protein.