How does M-k work?

[Kai Grossjohann]

Say I have this text snippet in LaTeX mode (AUC-TeX):

    \caption{Foo bar.  Quux quux.}

I position point after the first period and hit M-k:

    \caption{Foo bar.

I'm surprised that the "}" is gone.  I expected the "}" to stay.  Why
is this behavior good?  Can it be changed?  Is there another command
that does what I expect?  Can I change what I expect so that I'm not
surprised?

(If the sentence to kill is long, I might easily miss that there was a
parenthesis before, so my LaTeX code might end up wrong.)

Kai