CRYSTAL STRUCTURE OF THE ATP-DEPENDENT CLP PROTEASE CLPC FROM CLOSTRIDIUM DIFFICILE 3FES ATP BINDING PROTEIN, ALPHA-HELICAL BUNDLES, STRUCTURAL GENOMICS, PSI-2, PROTEIN STRUCTURE INITIATIVE, MIDWEST CENTER FOR STRUCTURAL GENOMICS, MCSG, ATP-BINDING, CHAPERONE, NUCLEOTIDE-BINDING, PROTEASE