Pyruvate kinase generates ATP in the cytoplasm during glycolysis. Consequently, phosphoenolpyruvate (PEP) is typically present in the cytoplasm. The concentration of PEP in the nucleus is extremely low. Figure . Tau protein provides ATP energy for its telomere transposition through the pyruvate kinase (PK) domain. The protein sequence rectangle displays the A-E rectangles, which represent the five PK domains. This diagram was drawn by IBS 1.0 .