Catalyzes a mechanistically unusual reaction, the ATP-dependent insertion of CO2 between the N7 and N8 nitrogen atoms of 7,8-diaminopelargonic acid (DAPA, also called 7,8-diammoniononanoate) to form a ureido ring (By similarity). This cyanobacterium does not encode bioA (which catalyzes the formation of the precursor for this reaction in the cannonical pathway), instead it encodes bioU, which replaces bioA and also performs the first half of the cannonical BioD reaction. Thus in this organism BioD has a different substrate (By similarity). (7R,8S)-7,8-diammoniononanoate + ATP + CO2 = (4R,5S)-dethiobiotin + ADP + 3 H(+) + phosphate (7R,8S)-8-amino-7-(carboxyamino)nonanoate + ATP = (4R,5S)-dethiobiotin + ADP + H(+) + phosphate Cofactor biosynthesis; biotin biosynthesis; biotin from 7,8-diaminononanoate: step 1/2. Homodimer. Belongs to the dethiobiotin synthetase family.