CRYSTAL STRUCTURE OF DOMAIN OF UNKNOWN FUNCTION WITH A CYSTATIN-LIKE FOLD (ZP_00111510.1) FROM NOSTOC PUNCTIFORME PCC 73102 AT 1.80 A RESOLUTION STRUCTURAL GENOMICS, UNKNOWN FUNCTION, ZP_00111510.1, DOMAIN OF UNKNOWN FUNCTION WITH A CYSTATIN- LIKE FOLD, JOINT CENTER FOR STRUCTURAL GENOMICS, JCSG, PROTEIN STRUCTURE INITIATIVE, PSI-2 2RGQ