EC Number   |
Posttranslational Modification |
Reference |
|---|
   3.1.26.3 | phosphoprotein |
Ec-RNase III is phosphorylated on serine in bacteriophage T7-infected cells, Ec-RNase III is phosphorylated on Ser33 and Ser34 in the N-terminal catalytic domain in vitro by purified serine/threonine-specific protein phosphotransferase activity (T7PK) targeting Ser33 and Ser34 in the N-terminal catalytic domain. Kinetic experiments reveal a 5fold increase in kcat and a 1.4fold decrease in Km following phosphorylation, providing a 7.4fold increase in catalytic efficiency. Phosphorylation does not change the rate of substrate cleavage under single-turnover conditions, indicating that phosphorylation enhances product release, which also is the rate-limiting step in the steady-state. Molecular dynamics simulations provide a mechanism for facilitated product release, in which the Ser33 phosphomonoester forms a salt bridge with the Arg95 guanidinium group, thereby weakening RNase III engagement of product. The simulations also show why glutamic acid substitution at either serine does not confer enhancement, thus underscoring the specific requirement for a phosphomonoester. T7PK phosphorylates serine in the alpha2-alpha3 loop of the RNase III catalytic domain |
752191 |
| 3.1.26.3 | phosphoprotein |
phosphorylation on a serine in the RNase III domain activates the enzyme, the covalent modification facilitates product release, which is the rate-limiting step in the catalytic pathway |
731020 |
| 3.1.26.3 | phosphoprotein |
RNase III undergoes serine phosphorylation in the T7 virus-infected cell, which enhances its catalytic activity by 3-5 fold |
751291 |
| 3.1.26.3 | phosphoprotein |
two phosphorylation sites at Ser300 and Ser302, which locates Drosha to the nucleus |
716372 |
