Subject: Are there any cyclized proteins?

I was wondering if there are any proteins where the polypeptide chains
intentionally link the N-terminus to the C-terminus to cyclize the chain?
I thought some protein must do this since there's always a free amino and
carboxy end floating around, but my TA didn't know of anything like this.

Or could you have a protein with a lot of prolines that kinks around the
ribosome as the peptide chain elongates so that it re-attaches with the
C-terminal end? 

Re: Are there any cyclized proteins?