Lindskog structure

Two stable bicarbonato complexes of bis(l,10-phenanthroline) copper(II) were reported for the first time by Mao et al. (44). These are akin to the Lipscomb and Lindskog structures of human carbonic anhydrase (HCA) (45). In the Lipscomb structure the bicarbonate acts as a bidentate ligand while in the Lindskog structure it is essentially coordinated to the metal center in unidentate fashion (Fig. 2). 

Fig. 2. [Cu(phen)2(0C02H)]+ N-N = 1,10-phenanthroline. 5 - Lipscomb structure 6 - Lindskog structure.

Theoretical work by Merz and co-workers" essentially follows the pathway in Scheme 8.7 and finds that the bicarbonate is bound in the Lipscomb model, with the Lindskog structure being an intermediate or transition state on the pathway to the more stable form. More recent theory" has emphasized the importance of H2O and other groups at the active site in facilitating the proton transfer reactions. It should be noted that the theoretical conclusions have changed and evolved with time" and must be viewed accordingly. Two X-ray structures with bicarbonate bound to CA I " and a CA II" mutant have been used to support the Lindskog structure. In simple models, both bidentate and monodentate HCOj" has been observed in Cu(II) complexes," while examples of bidentate Co(III)" and monodentate Ni(II)" coordination are known. These and other models have been reviewed recently." ... 

Cobalt(II) in metalloenzymes a report of structure-function relationships. S. Lindskog. Struct. Bonding (Berlin), 1970,8,154-196 (142). 

Lindskog S (1970) Cobalt(II) in Metalloenzymes. A Reporter of Structure-Function Relations. 8 153-196 Ling JH, see Hall DI (1973) 15 3-51... 

A. J. Bearden, W. R. Durnham Iron Electronic Configurations in Proteins Studies by Moss-bauer Spectroscopy. - K Wiitkrich Structural Studies of Hemes and Hemoproteins by Nuclear Magnetic Resonance Spectroscopy. -H. A 0. Hill,A. Roder, R. J. P. Williams The Chemical Nature and Reactivity of Cytochrome P-450. - S. Lindskog Cobalt (II) in Metalloenzymes. A Reporter of Structure-Function Relations. 

Lindskog and Malmstrom (1962) first succeeded in removing the zinc under sufficiently mild conditions to avoid denaturation. The zinc was complexed with phenan-throline and the resulting complex removed by dialysis. The apoenzyme was catalytically inactive and the activity could be restored by addition of one mole of zinc per mole of apoenzyme. ORD studies have shown that the apoenzyme and the native enzyme have the same gross teriary structure, confirming that the function of the zinc is not to stabilise the tertiary structure, but it is directly involved in the catalytic activity of the enzyme. 

S. Lindskog. 1997. Structure and mechanism of carbonic anhydrase Pharmacol. Ther. 74 1-20. (PubMed)... 

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