Not a problem as Contax made the MAM-1 Adapter for that very purpose (not to be confused with the NAM-1 Adapter). I believe that there are also several 3rd party adapters that do the same but are much less expensive.
YES, with an special adapter! At the time, I was using a Contax 645, I was very pleased with an adapted K-6 5,6/250mm MC TELEAR from the Ukraine! I never stopped the lens down using it on this camera. The lens is tack sharp, and I am still using this lens now, adapted on my Sony A7 and A6000!