This protein has been found so far only in the Archaea, and in particular in those archaea that lack a bacterial-type dihydropteroate synthase. The central region of this protein shows considerable homology to the amino-terminal half of dihydropteroate synthases, while the carboxyl-terminal region shows homology to the small, uncharacterized protein slr0651 of Synechocystis PCC6803. [Unknown function, General]