CRYSTAL STRUCTURE OF A PPR1-DNA COMPLEX : DNA RECOGNITION BY PROTEINS CONTAINING A ZN2CYS6 BINUCLEAR CLUSTER

摘要: PPR1 is a yeast transcription factor that contains six-cysteine, two-zinc (Zn) domain, homologous to similar structure in GAL4. Like GAL4, it binds DNA sites with conserved CGG triplets symmetrically placed near each end. Whereas the GAL4 site has 11 intervening base pairs, 6. The crystal of 95-residue fragment specific complex shows protein symmetrical 14-bp recognition as nonsymmetrical homodimer. An amino-terminal Zn domain interacts triplet end through major groove contacts, and carboxy-terminal residues mediate dimerization coiled-coil element an extended strand. A linker region, connecting coiled-coil, folds into beta-hairpin. This hairpin packs differently on two subunits leads striking asymmetry, which largely restricted regions protein. Comparison GAL4-DNA their specificities for different length are determined by preferred respective segments at ends coiled-coils. None these contact PPR1, they only sugar phosphate backbone We propose this novel mode selection employed other proteins contain Zn2Cys6 binuclear cluster.