PSI-Search (or PSISEARCH) is an iterative HOE-reduced profile Smith-Waterman sequence search.

The search method combines sensitive Smith-Waterman searching using SSEARCH with the PSI-BLAST profile construction strategy (blastpgp or psiblast) to find distantly related protein sequences. It includes options to reduce homologous over-extension (HOE) errors and is our most sensitive and selective similarity search tool.