@article {2636,
	title = {Investigation of the Catalytic Mechanism of a Synthetic DNAzyme with Protein-like Functionality: An RNaseA Mimic?},
	journal = {Journal of the American Chemical Society},
	volume = {131},
	number = {15},
	year = {2009},
	note = {ISI Document Delivery No.: 434IJTimes Cited: 3Cited Reference Count: 108Thomas, Jason M. Yoon, Jung-Ki Perrin, David M.},
	month = {Apr},
	pages = {5648-5658},
	type = {Article},
	abstract = {The protein enzyme ribonuclease A (RNaseA) cleaves RNA with catalytic perfection, although with little sequence specificity, by a divalent metal ion (M2+)-independent mechanism in which a pair of imidazoles provides general acid and base catalysis, while a cationic amine provides electrostatic stabilization of the transition state. Synthetic imitation of this remarkable organo-catalyst ("RNaseA mimicry") has been a longstanding goal in biomimetic chemistry. The 9(25)-11 DNAzyme contains synthetically modified nucleotides presenting both imidazole and cationic amine side chains, and catalyzes RNA cleavage with turnover in the absence of M2+ similarly to RNaseA. Nevertheless, the catalytic roles, if any, of the "proteinlike" functional groups have not been defined, and hence the question remains whether 925-11 engages any of these functionalities to mimic aspects of the mechanism of RNaseA. To address this question, we report a mechanistic investigation Of 925-11 Catalysis wherein we have employed a variety of experiments, such as DNAzyme functional group deletion, mechanism-based affinity labeling, and bridging and nonbridging phosphorothioate substitution of the scissile phosphate. Several striking parallels exist between the results presented here for 925-11 and the results of analogous experiments applied previously to RNaseA. Specifically, our results implicate two particular imidazoles in general acid and base catalysis and suggest that a specific cationic amine stabilizes the transition state via diastereoselective interaction with the scissile phosphate. Overall, 925-11 appears to meet the minimal criteria of an RNaseA mimic; this demonstrates how added synthetic functionality can expand the mechanistic repertoire available to a synthetic DNA-based catalyst.},
	keywords = {ACID-BASE CATALYSIS, CLEAVING DNA ENZYME, COMPLEX, CYTOSOLIC FREE MAGNESIUM, DELTA VIRUS RIBOZYME, DINUCLEAR ZN(II), DIVALENT METAL-IONS, HAIRPIN RIBOZYME CATALYSIS, HDV GENOMIC, IN-VITRO SELECTION, RIBONUCLEASE-A, RIBOZYME},
	isbn = {0002-7863},
	url = {<Go to ISI>://000265268100049},
	author = {Thomas, J. M. and Yoon, J. K. and Perrin,David M.}
}
@article {2285,
	title = {Probing General Base Catalysis in the Hammerhead Ribozyme},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {46},
	year = {2008},
	note = {ISI Document Delivery No.: 406QZTimes Cited: 8Cited Reference Count: 53Thomas, Jason M. Perrin, David M.},
	month = {Nov},
	pages = {15467-15475},
	type = {Article},
	abstract = {Recent structural and computational studies have shed new light on the catalytic mechanism and active site structure of the RNA cleaving hammerhead ribozyme. Consequently, specific ribozyme functional groups have been hypothesized to be directly involved in general/acid base catalysis. In order to test this hypothesis, we have developed an affinity label to identify the functional general base in the S. mansoni hammerhead ribozyme. The ribozyme was reacted with a substrate analogue bearing a 2{\textquoteright}-bromoacetamide group in place of the nucleophilic 2{\textquoteright}-hydroxyl group which would normally be deprotonated by a general base. The electrophilic 2{\textquoteright}-bromoacetamide group is poised to alkylate the general base, which is subsequently identified by footprinting analysis. Herein, we demonstrate alkylation of N1 of G12 in the hammerhead ribozyme in a pH and [Mg2+] dependent manner that is consistent with the native cleavage reaction. These results provide substantial evidence that deprotonated N1 of G12 functions directly as a general base in the hammerhead ribozyme; moreover, our experiments provide evidence that the pK(a) of G12 is perturbed downward in the context of the active site structure. We also observed other pH-independent alkylations, which do not appear to reflect the catalytic mechanism, but offer further insight into ribozyme conformation and structure.},
	keywords = {ACTIVE-SITE, CLEAVAGE, CRYSTAL-STRUCTURE, DELTA VIRUS RIBOZYME, HAIRPIN RIBOZYME, MECHANISM, METAL-ION, MONOVALENT CATIONS, NUCLEOBASE CATALYSIS, RNA},
	isbn = {0002-7863},
	url = {<Go to ISI>://000263311300051},
	author = {Thomas, J. M. and Perrin,David M.}
}
