Crystal structures of carbonic anhydrase (CA) isozymes I and II in complex with Cu2+-containing "two-prong" inhibitors and with derivatives of p-aminobenzenesulfonamide (pAEBS) and of p-carboxylbenzenesulfonamide (pCEBS) are reported here. These structures shed light on determinants of isozyme-specific inhibition of carbonic anhydrases as mediated by both specific, enthalpy-driven, and nonspecific, entropy-driven, interactions.
Additionally, the structure of F65A/Y131C murine CAV, covalently modified at cysteine residues with 4-chloromethylimidazole, is reported. The introduction of a methylimidazole (MI) group at residue C131 in the active site results in up to a 3-fold rate enhancement of CO2 hydration by the enzyme versus wild-type activity. This structure demonstrates that C131-MI acts as a proton shuttle to facilitate deprotonation of a zinc-bound water molecule to regenerate the nucleophilic zinc-bound hydroxide ion. A network of three hydrogen-bonded water molecules, across which proton transfer likely proceeds, bridges the zinc-bound water molecule and the C131-MI imidazole group. Comparison with other carbonic anhydrase crystal structures allows common features of catalytic proton shuttles to be outlined.
Furthermore, crystallization of the ribozyme ribonuclease P from Bacillus subtilis is reported here. Crystallization of the RNA subunit and of a complex containing both the RNA subunit and the product tRNA is reported, as well as initial progress in phasing the structure of the ribonuclease P holoenzyme, comprising a 130 kD RNA subunit and a 14 kD protein subunit. This represents the first report of crystallization of a ribonuclease P-product complex.
|Advisor:||Christianson, David W.|
|School:||University of Pennsylvania|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 68/04, Dissertation Abstracts International|
|Keywords:||Carbonic anhydrase, Ribonuclease P, Ribozymes|
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