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PMID 10944209
We report a strategy (called "tethering") to discover low molecular weight ligands ( approximately 250 Da) that bind weakly to targeted sites on proteins through an intermediary disulfide tether. A native or engineered cysteine in a protein is allowed to react reversibly with a small library of disulfide-containing molecules ( approximately 1,200 compounds) at concentrations typically used in drug screening (10 to 200 microM). The cysteine-captured ligands, which are readily identified by MS, are among the most stable complexes, even though in the absence of the covalent tether the ligands may bind very weakly. This method was applied to generate a potent inhibitor for thymidylate synthase, an essential enzyme in pyrimidine metabolism with therapeutic applications in cancer and infectious diseases. The affinity of the untethered ligand (K(i) approximately 1 mM) was improved 3,000-fold by synthesis of a small set of analogs with the aid of crystallographic structures of the tethered complex. Such site-directed ligand discovery allows one to nucleate drug design from a spatially targeted lead fragment.


Chirality underpins all life. Nineteen of the twenty amino acids contain at least one stereocenter, as do all nucelosides, sugars, and most metabolites. The very first fragment I ever found was chiral, but that is not typical, at least judged by those that...
If you want to visualize and manipulate crystallographic data there are plenty of options, such as PyMOL and OpenAstexViewer. However, powerful molecular graphics programs such as these have a learning curve associated with them, and sometimes its nice to get...
The tumor suppressor p53 is one of the cells very best friends. Just how good a friend it is becomes apparent when, just like in other relationships, this particular relationship turns sour. p53 is the master guardian angel of the genome and constitutes the...