Ctrlk would delete everything from the current position of the cursor to the end of line. Is there some equivalence to delete everything from the current position to the beginning of line?
For me Ctrl-0Ctrl-k does what you want. I think this is the default configuration, it's certainly not something I've modified.
If this doesn't work try Ctrl-u0Ctrl-k. Again, that seems to be Emacs' default behaviour on my installation (Emacs 24.x, Mac OS X).