To find the best lattice model representation of a given full atom protein structure is a hard computational problem. Several greedy methods have been suggested where results are usually biased and leave room for improvement. In this paper we formulate and implement a Constraint Programming method to refine such lattice structure models. We show that the approach is able to provide better quality solutions. The prototype is implemented in COLA and is based on limited discrepancy search. Finally, some promising extensions based on local search are discussed.