CRYSTAL STRUCTURE OF PUTATIVE SERINE-PYRUVATE AMINOTRANSFERASE (YP_263484.1) FROM PSYCHROBACTER ARCTICUM 273-4 AT 2.20 A RESOLUTION 3KE3 TRANSFERASE, PUTATIVE SERINE-PYRUVATE AMINOTRANSFERASE, STRUCTURAL GENOMICS, JOINT CENTER FOR STRUCTURAL GENOMICS, JCSG, PROTEIN STRUCTURE INITIATIVE, PSI-2, AMINOTRANSFERASE, PYRUVATE