STRUCTURE OF THE CO1E1 ROP PROTEIN AT 1.7 A RESOLUTION

Structural details of the Rop protein from plasmid ColE1 are presented, with a description of the X-ray crystal structure determination and refinement at a nominal resolution of 1.7 Å. The 63 amino acid protein is a dimer. Each monomer consists almost entirely of two alpha helices, the whole molecule forming a highly regular four-alpha-helix bundle. This may be approximated by a four-stranded rope with a radius of 7.0 Å, a left-handed helical twist and a pitch of 172.5 Å. The packing constraints for this novel type of coiled-coil structure are given. The protein acts in the control of plasmid replication via regulation of an RNA-RNA interaction in a manner not yet understood in atomic detail. © 1987.