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Starting with a query sequence of interest, the PSI-BLAST process operates by taking a query protein sequence and performing a standard BLASTP search, as described above. This search produces a number of hits having E values better than a certain set threshold. These hits, along with the initial, single-query sequence, are used to construct a PSSM in an automated fashion. As soon as the PSSM is constructed, the PSSM then serves as the query for doing a new search against the target database, using the collective characteristics of the identified sequences to find new, related sequences. The process continues, round by round, either until the search converges (meaning that no new sequences were found in the last round) or until the limit on the number of iterations is reached.