Characterization of molecular defects of HK-deficient patients. The domain structure of HK is shown. Solid lines indicate the size of the plasma proteins. The dotted lines indicate the size of the DNA that has the potential to make the protein. Williams trait (Williams) has a premature stop codon at amino acid (aa) 177 of the mature protein. The propositus (Proband) has no plasma HK as result of a single base pair deletion at amino acid 480 of the mature protein and the degeneration into a stop codon downstream. Fitzgerald trait (Fitzgerald) has identified protein antigen through amino acid 502 of the mature protein. Normal full-length HK is 626 amino acids in the mature, secreted protein.