期刊
JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY
卷 5, 期 1, 页码 67-74出版社
SPRINGER VERLAG
DOI: 10.1007/s007750050009
关键词
human immunodeficiency virus type 1 reverse transcriptase ribonuclease H domain; calorimetry; metal binding; mechanism; stoichiometry
资金
- NIAID NIH HHS [AI36219] Funding Source: Medline
- NIGMS NIH HHS [GM52263] Funding Source: Medline
Crystallographic studies of the Mn2+-doped RNase H domain of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) [1] have revealed two bound Mn2+ separated by approximately 4 Angstrom and surrounded by a cluster of four conserved carboxylates. Escherichia coli RNase H is structurally similar to the RNase H domain of HIV-1 RT, but requires one divalent metal cation for its activity [2, 3], implying either that the HIV-1 RT RNase H domain contrasts in its ability to bind two divalent metal ions, or that the crystallographic data reflect specific use of Mn2+ and/or the doping technique employed. Metal binding stoichiometry has been determined for Mn2+ and the biologically more relevant Mg2+ cation by solution calorimetric studies of native and recombinant p66/p51 HIV-1 RT. Three Mn2+ ions bind to HIV-1 RT ape-enzyme: one at the DNA polymerase and two at the RNase H catalytic center, the latter being consistent with crystallographic results. However, only one Mg2+ ion is bound in the RNase H catalytic center. Several mechanistic implications arise from these results, including the possibility of mutually exclusive Mg2+ binding sites that might be occupied according to the specific reaction being catalyzed by the multifunctional RNase H domain. The occurrence of distinct binding stoichiometries for Mg2+ and Mn2+ to multifunctional enzymes has previously been reported [4].
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