I am in a defunct LLC and we took a loan out using our houses as collateral. Now that the loan is in default what can be done to protect my house?

You should consult with an attorney, preferably one who could also help you with bankruptcy, immediately.

1) Exactly how much you personally are liable for under the loan (e.g. 1/3 or the full amount) will depend on the loan agreement--it is possible that you may be liable for the full amount, even though you are only a 1/3 owner.  A lawyer should examine the documents for you.

2) If the amount owed is sizeable, expect there is a reasonably good chance the bank will go after the collateral to satisfy it--that's why it wanted collateral in the first place.

3) If you have assumed $300k of credit card in addition to being liable on some or all of a bank loan large enough the bank wanted houses as collateral, you may wish to consider bankruptcy as an option.

4) You may be able to sue your co-owners if they have defaulted on their obligations, leaving you holding the bag, but if they have no or little assets or income at this point, even if you win, you could not collect.