General acid-base catalysis in the mechanism of a hepatitis delta virus ribozyme
S Nakano, DM Chadalavada, PC Bevilacqua - Science, 2000 - science.org
S Nakano, DM Chadalavada, PC Bevilacqua
Science, 2000•science.orgMany protein enzymes use general acid-base catalysis as a way to increase reaction rates.
The amino acid histidine is optimized for this function because it has ap K a (where K a is the
acid dissociation constant) near physiological pH. The RNA enzyme (ribozyme) from
hepatitis delta virus catalyzes self-cleavage of a phosphodiester bond. Reactivity-pH profiles
in monovalent or divalent cations, as well as distance to the leaving-group oxygen, implicate
cytosine 75 (C75) of the ribozyme as the general acid and ribozyme-bound hydrated metal …
The amino acid histidine is optimized for this function because it has ap K a (where K a is the
acid dissociation constant) near physiological pH. The RNA enzyme (ribozyme) from
hepatitis delta virus catalyzes self-cleavage of a phosphodiester bond. Reactivity-pH profiles
in monovalent or divalent cations, as well as distance to the leaving-group oxygen, implicate
cytosine 75 (C75) of the ribozyme as the general acid and ribozyme-bound hydrated metal …
Many protein enzymes use general acid-base catalysis as a way to increase reaction rates. The amino acid histidine is optimized for this function because it has a pK a (whereK a is the acid dissociation constant) near physiological pH. The RNA enzyme (ribozyme) from hepatitis delta virus catalyzes self-cleavage of a phosphodiester bond. Reactivity-pH profiles in monovalent or divalent cations, as well as distance to the leaving-group oxygen, implicate cytosine 75 (C75) of the ribozyme as the general acid and ribozyme-bound hydrated metal hydroxide as the general base in the self-cleavage reaction. Moreover, C75 has a pK a perturbed to neutrality, making it “histidine-like.” Anticooperative interaction is observed between protonated C75 and a metal ion, which serves to modulate the pK a of C75. General acid-base catalysis expands the catalytic repertoire of RNA and may provide improved rate acceleration.
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