HEADSC 2onx SEQCRD A N ASN ASN 1 1 C C 0 SEQCRD A N ASN ASN 2 2 C C 0 SEQCRD A Q GLN GLN 3 3 C C 0 SEQCRD A Q GLN GLN 4 4 C C 0 PARAME method XRAY PARAME resolution 1.520 PARAME R-factor 0.175 PARAME FreeR-factor 0.202