The binding of platinum hexahalides (Cl, Br and I) to hen egg-white lysozyme and the chemical transformation of the PtI₆octahedral complex to a PtI₃moiety bound to His15

Abstract

The platinum hexahalides have an octahedral arrangement of six halogen atoms bound to a Pt centre, thus having an octahedral shape that could prove to be useful in interpreting poor electron-density maps. In a detailed characterization, PtI6 chemically transformed to a square-planar PtI3 complex bound to the Nδ atom of His15 of HEWL was also observed, which was not observed for PtBr6 or PtCl6.

Crystallography and chemistry should always go together: a cautionary tale of protein complexes with cisplatin and carboplatin

“…Structural information about the binding of cisplatin to several model proteins has been reported during the last eight years. Whereas the vast majority of structures represent complexes with the tetragonal or triclinic forms of hen eggwhite lysozyme (HEWL; Casini et al, 2007;Tanley, Schreurs, Kroon-Batenburg & Helliwell, 2012b;Tanley, Schreurs, Kroon-Batenburg, Meredith et al, 2012;Tanley et al, 2014;Tanley & Helliwell, 2014a), data are also available for complexes with bovine Cu,Zn superoxide dismutase (SOD; Calderone et al, 2006;Banci et al, 2012), the human copper-transport protein ATOX1 (Boal & Rosenzweig, 2009), bovine pancreatic RNase A (Messori & Merlino, 2014) and Plasmodium falciparum glutaredoxin 1 (PfGrx1; unpublished work). All available structures of carboplatin involve complexes with the tetragonal, monoclinic or trigonal forms of HEWL (Tanley, Schreurs, Kroon-Batenburg & Helliwell, 2012a;Tanley, Schreurs, Kroon-Batenburg, Meredith et al, 2012;Tanley et al, 2014;Tanley & Helliwell, 2014b).…”

X-ray diffraction in temporally and spatially resolved biomolecular science

“…So, where we can expect difficult to interpret electron density maps, and their time-resolved changes in biochemical reactions, these 'marker well-shaped complexes' will offer a start to electron density map interpretations. 9 The break-up of platinum hexabromide, even when cryocooled, upon prolonged X-ray irradiation, akin to the UV study, 11 was reported previously. 13 Here we report the HEWL with bound PtBr 6 at room temperature also upon prolonged X-ray irradiation.…”

“…The refined structure of the HEWL PtI 6 data set 0 PDB code is 4owc (ref. 9). The protein model shown here is 2W1Y and the maps are each rigid body 2W1Y model refinement Fo-Fc 'omit' (i.e.…”

“…7 In considering these challenges and the clear advantage of being able to measure X-ray diffraction from a single molecule, with or without temporal resolved structural changes, we have studied in detail a class of metal complexes, the platinum hexahalides, as well as the tantalum bromide cluster when bound to hen egg-white lysozyme (HEWL) as a test protein crystal including their 'X-ray-photo-dynamics. 8,9 These metal clusters have the major advantage of being very recognisable shapes (octahedral and pseudo spherical). So, where we can expect difficult to interpret electron density maps, and their time-resolved changes in biochemical reactions, these 'marker well-shaped complexes' will offer a start to electron density map interpretations.…”

“…So, where we can expect difficult to interpret electron density maps, and their time-resolved changes in biochemical reactions, these 'marker well-shaped complexes' will offer a start to electron density map interpretations. 9 A further approach is to investigate the X-ray laser beam diffraction strength of a well scattering nano-cluster; an example from nature being the iron containing ferritin (which has 2000 iron atoms in ferrihydrite form within a protein multisubunit shell). 10 Another example would be, in a bionanotechnology approach, an encapsulated metal core within a virus protein shell.…”