TRANSPORT PROTEIN, RECEPTOR FAMILY LIGAND BINDING REGION, STRUCTURAL GENOMICS, JOINT CENTER FOR STRUCTURAL GENOMICS, JCSG, PROTEIN STRUCTURE INITIATIVE, PSI-2 CRYSTAL STRUCTURE OF AN ABC-TYPE BRANCHED-CHAIN AMINO ACID TRANSPORTER (RPA4397) FROM RHODOPSEUDOMONAS PALUSTRIS CGA009 AT 1.50 A RESOLUTION 3N0X