We investigate how does the range of attraction of a coarse-grained protein model affect cooperativity of folding transition. Free-energy landscapes of chymotrypsin inhibitor 2 (CI2) and bovine pancreatic trypsin inhibitor (BPTI) are obtained by a lattice protein model with Go-like interaction. With the range of attraction being varied as a parameter, we find that a short-range nature of interaction is important for cooperativity. BPTI exhibits a folding intermediate whose structure is similar to that observed experimentally, when the range of attractions is appropriately set. Thus subdomain structure is determined mainly by the native topology. (c) 2006 Elsevier B.V. All rights reserved.