Grant: Operating Grant

The mucopolysaccharidoses (MPS) are a group of devastating genetic diseases affecting about 1 in 25,000 individuals; in their most severe forms, they lead to death sometime during the first ten years of life. Mutations in the gene encoding the lysosomal enzyme alpha- L-iduronidase (IDUA) are the primary cause of one of the MPSs known as mucopolysaccharidosis type I (MPS I). In order to correlate the greater than 100 disease-causing mutations with disease severity amongst MPS I patients, it is of paramount importance to understand the effect that they have on IDUA. This would shed some light as to why certain single-change ('point') mutations produce a severely abnormal IDUA enzyme and thus lead to severe MPS I disease, while other point mutations produce an IDUA enzyme with only minor structural perturbations, and are manifested by attenuated forms of the disease. As the 3-D structure of IDUA is not known this correlation cannot be made accurately. Therefore, the primary objective of this proposal is to determine the 3-D structure of IDUA so that the known genetic changes can be pinpointed on the structure of IDUA and their consequences can be understood. In order to produce enough enzyme for this structure determination we are proposing to make human IDUA in plants. The 3-D structure of IDUA will be determined by the method of X-ray Crystallography. Once the structure of IDUA is known it will be possible to elucidate the enzymatic mechanism and therefore to understand in detail the effects that the various mutations have on the enzymatic activity. In addition, the structure of IDUA will be used to design small molecules that will help the mutant enzymes to fold into a functional conformation that will ultimately allow the mutant IDUA molecules to have enhanced enzymatic activity. For some patients suffering from intermediate or attenuated forms of MPS I disease, these so-called 'pharmacological chaperones' could be used as effective therapies.