Mechanism of bacteriophage T4 DNA holoenzyme assembly: the 44/62 protein acts as a molecular motor.


The role of ATP hydrolysis by the 44/62 protein in formation of the ...
The role of ATP hydrolysis by the 44/62 protein in formation of the stable holoenzyme DNA replication complex has been further elucidated by specifically examining the role that the 44/62 protein plays in loading the 45 protein onto the DNA substrate. A stable phospho-45 protein or phosphorylated holoenzyme complex was not detected or isolated, suggesting that the 44/62 protein may not act as a protein kinase. Product and dead-end inhibition data are consistent with an ordered kinetic mechanism with respect to product release in which phosphate is released from the 44/62 protein prior to ADP. Positional isotope effect studies support this mechanism and failed to demonstrate that ATP hydrolysis by the 44/62 protein is reversible. Steady-state ATPase assays using aluminum tetrafluoride as an inhibitor are also consistent with release of ADP being partially rate-limiting. Aluminum tetrafluoride acts to trap ADP on the enzyme after turnover, forming a stable transition state analog that dissociates slowly from the enzyme. Processive DNA synthesis does not occur using the accessory proteins in the presence of pre- or post-hydrolysis analogs of ATP nor in the presence of ADP-AlF4, indicating that turnover of the 44/62 protein is absolutely required for formation of the holoenzyme complex. Collectively, data obtained regarding ATP hydrolysis by the 44/62 protein are described in terms of the clamp loading protein functioning as a molecular motor, similar to other systems including myosin and kinesin.




Accessory Proteins/Complexes

One line summary:

ATP hydrolysis by 44/62 protein shows the clamp loading protein works in similarity to molecular motors like the myosin and kinesin system.


new topics/pols set partial results complete validated


No results available for this paper.

Entry validated by:

Using Polbase tables:


Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).


It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.