%0 Journal article %A Mehr, Alexander %A Henneberg, Fabian %A Chari, Ashwin %A Görlich, Dirk %A Huyton, Trevor %T The copper(II)‐binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography %R 10.1107/S2059798320013741 %R 10.23689/fidgeo-4112 %J Acta Crystallographica Section D %V 76 %N 12 %I International Union of Crystallography %X The growth of diffraction‐quality crystals and experimental phasing remain two of the main bottlenecks in protein crystallography. Here, the high‐affinity copper(II)‐binding tripeptide GHK was fused to the N‐terminus of a GFP variant and an MBP‐FG peptide fusion. The GHK tag promoted crystallization, with various residues (His, Asp, His/Pro) from symmetry molecules completing the copper(II) square‐pyramidal coordination sphere. Rapid structure determination by copper SAD phasing could be achieved, even at a very low Bijvoet ratio or after significant radiation damage. When collecting highly redundant data at a wavelength close to the copper absorption edge, residual S‐atom positions could also be located in log‐likelihood‐gradient maps and used to improve the phases. The GHK copper SAD method provides a convenient way of both crystallizing and phasing macromolecular structures, and will complement the current trend towards native sulfur SAD and MR‐SAD phasing. %U http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/8452 %~ FID GEO-LEO e-docs