Solid-State Structural Characterization of Cutinase–ECE-Pincer–Metal Hybrids

✍ Scribed by Lucy Rutten; Birgit Wieczorek; Jean-Paul B. A. Mannie; Cornelis A. Kruithof; Harm P. Dijkstra; Maarten R. Egmond; Martin Lutz; Robertus J. M. Klein Gebbink; Piet Gros; Gerard van Koten

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 938 KB
• Volume: 15
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200801995

✦ Synopsis

Abstract

Crystal‐clear structures: The first crystal structures of organometallic pincer–cutinase hybrids (see figure) provide insight into the 3D structural arrangement of both the protein and the organometallic pincer moiety, and reveal different binding modes for different pincers.magnified image

The first crystal structures of lipases that have been covalently modified through site‐selective inhibition by different organometallic phosphonate‐pincer–metal complexes are described. Two ECE‐pincer‐type d^8^‐metal complexes, that is, platinum (1) or palladium (2) with phosphonate esters (ECE=[(EtO)‐(O)P(‐O‐C~6~H~4~‐(NO~2~)‐4)(‐C~3~H~6~‐4‐(C~6~H~2~‐(CH~2~E)~2~)]^−^; E=NMe~2~ or SMe) were introduced prior to crystallization and have been shown to bind selectively to the Ser^120^ residue in the active site of the lipase cutinase to give cut‐1 (platinum) or cut‐2 (palladium) hybrids. For all five presented crystal structures, the ECE‐pincer–platinum or –palladium head group sticks out of the cutinase molecule and is exposed to the solvent. Depending on the nature of the ECE‐pincer–metal head group, the ECE‐pincer–platinum and –palladium guests occupy different pockets in the active site of cutinase, with concomitant different stereochemistries on the phosphorous atom for the cut‐1 (S~P~) and cut‐2 (R~P~) structures. When cut‐1 was crystallized under halide‐poor conditions, a novel metal‐induced dimeric structure was formed between two cutinase‐bound pincer–platinum head groups, which are interconnected through a single μ‐Cl bridge. This halide‐bridged metal dimer shows that coordination chemistry is possible with protein‐modified pincer–metal complexes. Furthermore, we could use NCN‐pincer–platinum complex 1 as site‐selective tool for the phasing of raw protein diffraction data, which shows the potential use of pincer–platinum complex 1 as a heavy‐atom derivative in protein crystallography.