SNAP output for PDB entry 6p0s [SNAP web server]

PDB-id

6p0s; SNAP-derived features in text and JSON formats; DNAproDB

Class

DNA binding protein-DNA

Method

X-ray (2.7 Å)

Summary

Crystal structure of ternary DNA complex "fx2" containing e. coli fis and phage lambda xis

Reference

Hancock SP, Cascio D, Johnson RC (2019): "Cooperative DNA binding by proteins through DNA shape complementarity." Nucleic Acids Res., 47, 8874-8887. doi: 10.1093/nar/gkz642.

Abstract

Localized arrays of proteins cooperatively assemble onto chromosomes to control DNA activity in many contexts. Binding cooperativity is often mediated by specific protein-protein interactions, but cooperativity through DNA structure is becoming increasingly recognized as an additional mechanism. During the site-specific DNA recombination reaction that excises phage λ from the chromosome, the bacterial DNA architectural protein Fis recruits multiple λ-encoded Xis proteins to the attR recombination site. Here, we report X-ray crystal structures of DNA complexes containing Fis + Xis, which show little, if any, contacts between the two proteins. Comparisons with structures of DNA complexes containing only Fis or Xis, together with mutant protein and DNA binding studies, support a mechanism for cooperative protein binding solely by DNA allostery. Fis binding both molds the minor groove to potentiate insertion of the Xis β-hairpin wing motif and bends the DNA to facilitate Xis-DNA contacts within the major groove. The Fis-structured minor groove shape that is optimized for Xis binding requires a precisely positioned pyrimidine-purine base-pair step, whose location has been shown to modulate minor groove widths in Fis-bound complexes to different DNA targets.