I-TASSER (Iterative Threading ASSEmbly Refinement) is a bioinformatics method for predicting three-dimensional structure model of protein molecules from amino acid sequences. It detects structure templates from the Protein Data Bank by a technique called fold recognition (or threading). The full-length structure models are constructed by reassembling structural fragments from threading templates using replica exchange Monte Carlo simulations. I-TASSER is one of the most successful protein structure prediction methods in the community-wide CASP experiments.
I-TASSER has been extended for structure-based protein function predictions, which provides annotations on ligand binding site, gene ontology and enzyme commission by structurally matching structural models of the target protein to the known proteins in protein function databases. It has an on-line server built in the Yang Zhang Lab at the University of Michigan, Ann Arbor, allowing users to submit sequences and obtain structure and function predictions. A standalone package of I-TASSER is available for download at the I-TASSER website.