title: Solid-state structural characterization of cutinase-ECE-pincer-metal hybrids.
abstract: 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 mu-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.
authors.affiliation: Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Lucy
authors.initials: L
authors.lastname: Rutten
authors.forename: Birgit
authors.initials: B
authors.lastname: Wieczorek
authors.forename: Jean-Paul B A
authors.initials: JP
authors.lastname: Mannie
authors.forename: Cornelis A
authors.initials: CA
authors.lastname: Kruithof
authors.forename: Harm P
authors.initials: HP
authors.lastname: Dijkstra
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Egmond
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.forename: Robertus J M
authors.initials: RJ
authors.lastname: Klein Gebbink
authors.forename: Piet
authors.initials: P
authors.lastname: Gros
authors.forename: Gerard
authors.initials: G
authors.lastname: van Koten
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D009942:Organometallic Compounds; D010984:Platinum; D010165:Palladium; D002265:Carboxylic Ester Hydrolases; C019952:cutinase