Keyframing in PPro is a little horsey compared to keyframing in After Effects--which is interesting because I think they're practically the same effects/animation engine. When I want to align keyframes from different animated effects, here's what I've been doing:
1) Select the keyframe you want to move to a different position in time. Hit Ctrl-X to cut it--it'll disappear into memory.
2) Use the keyframe navigator for the animated parameter you want to sync to in order to jump to the keyframe that represents the exact point in time you want to animate to (eesh... that sounds more complicated than it is).
3) Press Ctrl-V to paste in the keyframe that's in memory. It will reappear in the parameter you're trying to sync.
It's pretty quick once you get used to it, but having the ability to Shift-drag and snap keyframes into place, like in AE, would be lovely.