Ultrastructure of pig renal glutaminase. Evidence for conformational changes during polymer formation

Highly purified pig renal glutaminase has been examined by electron microscopy. It is demonstrated that the Tris·HCl form of the enzyme contains cylindrical particles with a diameter of about 60 Å and a length of about 82 Å. Treatment of the Tris·HCl form of the enzyme with sodium dodecyl sulphate and mercapto-ethanol, followed by polyacrylamide gel electrophoresis in sodium dodecyl sulphate, shows that the enzyme contains two types of sub units with molecular weights of 53,000 and 61,000. In agreement with earlier data, it is further demonstrated that the phosphate form is a simple dimer of the Tris·HCl form. Evidence that major conformational changes are involved in the formation of large, helical polymers of the enzyme described earlier, is also presented.