title: FastBLAST: homology relationships for millions of proteins.
abstract: BACKGROUND
  All-versus-all BLAST, which searches for homologous pairs of sequences in a database of proteins, is used to identify potential orthologs, to find new protein families, and to provide rapid access to these homology relationships. As DNA sequencing accelerates and data sets grow, all-versus-all BLAST has become computationally demanding.
  
  
  RESULTS
  We present FastBLAST, a heuristic replacement for all-versus-all BLAST that relies on alignments of proteins to known families, obtained from tools such as PSI-BLAST and HMMer. FastBLAST avoids most of the work of all-versus-all BLAST by taking advantage of these alignments and by clustering similar sequences. FastBLAST runs in two stages: the first stage identifies additional families and aligns them, and the second stage quickly identifies the homologs of a query sequence, based on the alignments of the families, before generating pairwise alignments. On 6.53 million proteins from the non-redundant Genbank database ("NR"), FastBLAST identifies new families 25 times faster than all-versus-all BLAST. Once the first stage is completed, FastBLAST identifies homologs for the average query in less than 5 seconds (8.6 times faster than BLAST) and gives nearly identical results. For hits above 70 bits, FastBLAST identifies 98% of the top 3,250 hits per query.
  
  
  CONCLUSIONS
  FastBLAST enables research groups that do not have supercomputers to analyze large protein sequence data sets. FastBLAST is open source software and is available at http://microbesonline.org/fastblast.
authors.affiliation: Physical Biosciences Divison, Lawrence Berkeley National Laboratory, Berkeley, California, USA. morgannprice@yahoo.com
authors.forename: Morgan N
authors.initials: MN
authors.lastname: Price
authors.forename: Paramvir S
authors.initials: PS
authors.lastname: Dehal
authors.forename: Adam P
authors.initials: AP
authors.lastname: Arkin
mesh_terms: D000465:Algorithms; D000818:Animals; D030561:Databases, Nucleic Acid; D030562:Databases, Protein; D004526:Efficiency; D006801:Humans; D005810:Multigene Family; D011506:Proteins / Q000032:analysis / Q000737:chemistry*; D016415:Sequence Alignment / Q000379:methods*; D020539:Sequence Analysis, Protein / Q000379:methods; D017386:Sequence Homology, Amino Acid; D012984:Software
chemical_list: D011506:Proteins