Catalytic sequence homologies around

The amino acid sequence of the enzyme is homologous with those of the pancreatic enzymes and has been shown by model building to be compatible with a chymotrypsin-like three-dimensional structure and catalytic site (36). The homology in sequence is particularly well marked around His-57. The enzyme s catalytic properties are virtually indistinguishable from those of pancreatic elastase. 

All P-class ion pumps possess two identical catalytic a subunits that contain an ATP-blndlng site. Most also have two smaller (3 subunits that usually have regulatory functions. During the transport process, at least one of the a subunits is phosphorylated (hence the name P class), and the transported ions are thought to move through the phosphorylated subunit. The sequence around the phosphorylated residue is homologous in different pumps. This class Includes the Na /K ATPase in the plasma membrane, which maln-... 

---