Crystallization and molecular-replacement studies of a recombinant antigen-binding fragment complexed with single-stranded DNA

Anti-DNA antibodies have been implicated in autoimmune diseases and also serve as models for understanding protein-DNA recognition. Crystals of a recombinant antigen-binding fragment (Fab) complexed with dT₅ have been obtained and initial phases have been determined using molecular replacement. The crystals diffract to 2.1 Å resolution and occupy space group P6₅22, with unit-cell parameters a = 171.8, c = 144.6 Å; there are two Fabs per asymmetric unit. X-PLORdirect rotation-function calculations followed by Patterson correlation filtering were successful when using a Fab search model; however, they failed when using the individual variable and conserved domains of the Fab as search models. AMoRe successfully identified the correct solution in cases where X-­PLOR failed.