[modeller_usage] modelling of sequence without structural template.

hello, can anybody suggest me anything about my problem? i am trying to model the structure of an oxidoreductase enzyme, for which thetemplate is of lenth shorter than the query sequence. last 47 amino acid residues at c-terminus of the protein didnot match wiht any template structure, and there are chances of these residues to be involved in formation of active site. so is there any method by which i can model this lenght of residues without alignment with any 3d structure?