IMPALA: matching a protein sequence against a collection of PSI-BLAST-constructed position-specific score matrices

A A Schäffer, Y I Wolf, C P Ponting, E V Koonin, L Aravind, S F Altschul

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

MOTIVATION: Many studies have shown that database searches using position-specific score matrices (PSSMs) or profiles as queries are more effective at identifying distant protein relationships than are searches that use simple sequences as queries. One popular program for constructing a PSSM and comparing it with a database of sequences is Position-Specific Iterated BLAST (PSI-BLAST).

RESULTS: This paper describes a new software package, IMPALA, designed for the complementary procedure of comparing a single query sequence with a database of PSI-BLAST-generated PSSMs. We illustrate the use of IMPALA to search a database of PSSMs for protein folds, and one for protein domains involved in signal transduction. IMPALA's sensitivity to distant biological relationships is very similar to that of PSI-BLAST. However, IMPALA employs a more refined analysis of statistical significance and, unlike PSI-BLAST, guarantees the output of the optimal local alignment by using the rigorous Smith-Waterman algorithm. Also, it is considerably faster when run with a large database of PSSMs than is BLAST or PSI-BLAST when run against the complete non-redundant protein database.

Original languageEnglish
Pages (from-to)1000-11
Number of pages12
Issue number12
Publication statusPublished - Dec 1999

Keywords / Materials (for Non-textual outputs)

  • Algorithms
  • Bacterial Proteins
  • Databases, Factual
  • False Negative Reactions
  • False Positive Reactions
  • Information Storage and Retrieval
  • Odds Ratio
  • Sequence Alignment
  • Sequence Analysis, Protein
  • Sequence Homology
  • Software


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