The default readline binding for
beginning-of-line is Ctrla. As this conflicts with
screen's command prefix, you can either rebind the screen prefix, as suggested by Johnny, or include another binding in your
.inputrc to map the readline behaviour to another keybind, for example to map the same behaviour to Alta, you could use:
This will allow you to use either Ctrl or Alt a outside of
screen and Alta within.
All of the readline bindings can be customized for both Emacs (the default) or vi mode.
A full list of all of the readline commands is availbale here: