How is folding ever an option here? With a $265 4bet, you've got most of your stack in the middle ($450 effective stack size). When villain 5bet shoves, he probably has a premium pair JJ+/AK, but we don't need too much equity to be profitable. We are only losing to EXACTLY AA/KK, and not by much (the EV is -$18.50 according to my calculations). If there is even a chance he's shoving QQ (which of course there is), it becomes a no brainer with the price we are getting. Maybe I'm missing something...
I do agree that the 4bet is extremely large, but that makes us more than pot committed. Unfortunately, villain probably knows he has no fold equity and is shoving for pure value, which tightens his range. I use Flopzilla's Holdeq calculator, and if we can add QQ to villain's range a mere 50% of the time, we get enough equity to call.
P.S. I'm new to the forum, and still getting the hang of higher level thinking in poker. If you disagree, please let me know. I'm still learning