發展CarbonicAnhydraseIX抑制劑當為抗癌的先導化合物研究(3/3)

Small molecule ligands should recognize key arrangement of particular amino acids while specifically binding to therecognized site. Usually the chemical structure of the ligand is varied to design a compound that would stronglyand selectively bind to the active site of a target enzyme with a goal of making it a drug. Human carbonic anhydraseisoform XII (CA XII) is an anticancer target, but since the overall fold of CA proteins is very similar, it is difficult to design inhibitors that would selectively inhibit only CA XII. Here we probe the recognition in reverse order by mutating the key six amino acids of human CA XII into CA II and observe the switch in recognition byover 60 compounds, i.e., the compounds that bind CA XII more strongly than CA II, switched their preference andbound more strongly to CA II and vice versa. The chimeric protein, chCA XII, based entirely on CA II, but containing the six key amino acids from CA XII, started to behave as CA XII in its compound recognition profile. The compounds also changed their structural arrangement in CA II to resemble CA XII as shown by X-ray crystallography of the compound binding orientation to CA II, CA XII and chCA XII. The chimeric chCA XII protein, mimicking CA XII, is a good model for drug design targeting CA XII and demonstrates the structure-activity relations of the mutated protein.