3A4I CRYSTAL STRUCTURE OF GMP SYNTHETASE PH1347 FROM PYROCOCCUS HORIKOSHII OT3 LIGASE, ATP PYROPHOSPHATASE, GLUTAMINE AMIDOTRANSFERASE, GMP SYNTHETASE, PURINE NUCLEOTIDE BIOSYNTHESIS, ATP-BINDING, GMP BIOSYNTHESIS, NUCLEOTIDE-BINDING, PURINE BIOSYNTHESIS