What is the equivalent of gksudo in Kubuntu/KDE?

The Kubuntu/KDE equivalent of gksudo is kdesudo. You can use this in the terminal or via the graphical command box on the top of the screen (Alt-F2).

When you do this, or otherwise launch an application which requires root privileges, you will get a kdesudo popup like this:

Note: If you are not getting this box with GUI applications, it may indicate a problem with the way the KDE desktop environment was installed. Please try reinstalling kubuntu-desktop if you are not using Kubuntu.

Now it is kdesu,

Example, If I want to use Matlab, and I want to run it as sudo user then I would type in: kdesu matlab, which would open a GUI window for taking my password as input.