PSI BLAST

• PSI - BLAST - (Position Specific Iterated BLAST) provides a new automatic "profile like" search. The program first performs a gapped BLAST search of the database. The significant alignments are then used by the program to construct a position specific score matrix(PSSM) . This matrix replaces the query sequence in the next round of database searching. The program may be iterated until no new significant alignments are found.