title: Within the twilight zone: a sensitive profile-profile comparison tool based on information theory.
abstract: This paper presents a novel approach to profile-profile comparison. The method compares two input profiles (like those that are generated by PSI-BLAST) and assigns a similarity score to assess their statistical similarity. Our profile-profile comparison tool, which allows for gaps, can be used to detect weak similarities between protein families. It has also been optimized to produce alignments that are in very good agreement with structural alignments. Tests show that the profile-profile alignments are indeed highly correlated with similarities between secondary structure elements and tertiary structure. Exhaustive evaluations show that our method is significantly more sensitive in detecting distant homologies than the popular profile-based search programs PSI-BLAST and IMPALA. The relative improvement is the same order of magnitude as the improvement of PSI-BLAST relative to BLAST. Our new tool often detects similarities that fall within the twilight zone of sequence similarity.
authors.affiliation: Department of Structural Biology, Fairchild Bldg. D-109, Stanford University, CA 94305, USA. golan@cs.cornell.edu
authors.forename: Golan
authors.initials: G
authors.lastname: Yona
authors.forename: Michael
authors.initials: M
authors.lastname: Levitt
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D019295:Computational Biology / Q000379:methods*; D030562:Databases, Protein; D007257:Information Theory; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D012107:Research Design; D012680:Sensitivity and Specificity; D016415:Sequence Alignment / Q000379:methods; D017386:Sequence Homology, Amino Acid; D012984:Software
chemical_list: D011506:Proteins