Linked Life Data

12534291

Source:http://linkedlifedata.com/resource/pubmed/id/12534291

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2003-1-21
pubmed:abstractText
RNase H degrades the RNA moiety in DNA:RNA hybrid in a divalent metal ion dependent manner. It is essential to understand the role of metal ion in enzymatic mechanism. One of the key points in this study is how many metal ions are involved in the enzyme catalysis. Accordingly, either one-metal binding mechanism or two-metal binding mechanism is proposed. We have studied the thermodynamic properties of four metal ions (Mg(2+), Mn(2+), Ca(2+), and Ba(2+)) binding to Methanococcus jannaschii RNase HII using isothermal titration calorimetry. All of the four metal ions were found to bind Mj RNase HII with 1:1 stoichiometry in the absence of substrate. Together with enzymatic activity assay data, we propose that only one metal ion binding to the enzyme in catalytic process. We also studied the pH dependence of metal binding and enzyme activity and found that at pH 6.5, Mg(2+) did not bind to the enzyme without the substrate but still activated the enzyme to about 2% of its maximum activity (in 10 mM Mn(2+) at pH 8). This implies that the substrate may also be incorporated in metal ion binding and help to position the metal ion. To find which acidic residues correspond to metal ion binding, we also studied the binding thermodynamics and enzymatic activity assay of four mutants: D7N, E8Q, D112N, and D149N in the presence of Mn(2+). The thermodynamic parameters are least affected for the D149N mutant, which has a very low enzymatic activity. This indicates that Asp149 is essential for the enzymatic activity. On the basis of all these observations, we suggest a metal binding model in which D7, E8, and D112 bind the metal ion and D149 activates a water molecule to attack the P-O bond in the RNA chain of the substrate.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
28
pubmed:volume
42
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
785-91
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Metal ion binding and enzymatic mechanism of Methanococcus jannaschii RNase HII.
pubmed:affiliation
State Key Laboratory for Structural Chemistry Studies of Stable and Unstable Species, Institute of Physical Chemistry, College of Chemistry, Peking University, Beijing 100871, China.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't