Improving the accuracy of PSI-BLAST protein database searches with composition-based statistics and other refinements
Alejandro A. Schäffer,L. Aravind,Thomas L. Madden,Sergei Shavirin,John L. Spouge,Yuri I. Wolf,Eugene V. Koonin,Stephen F. Altschul +7 more
TLDR
The use of composition-based statistics is particularly beneficial for large-scale automated applications of PSI-BLAST, and the use, for each database sequence, of a position-specific scoring system tuned to that sequence's amino acid composition.Abstract:
PSI-BLAST is an iterative program to search a database for proteins with distant similarity to a query sequence. We investigated over a dozen modifications to the methods used in PSI-BLAST, with the goal of improving accuracy in finding true positive matches. To evaluate performance we used a set of 103 queries for which the true positives in yeast had been annotated by human experts, and a popular measure of retrieval accuracy (ROC) that can be normalized to take on values between 0 (worst) and 1 (best). The modifications we consider novel improve the ROC score from 0.758± 0.005 to 0.895 ± 0.003. This does not include the benefits from four modifications we included in the ‘baseline’ version, even though they were not implemented in PSI-BLAST version 2.0. The improvement in accuracy was confirmed on a small second test set. This test involved analyzing three protein families with curated lists of true positives from the non-redundant protein database. The modification that accounts for the majority of the improvement is the use, for each database sequence, of a positionspecific scoring system tuned to that sequence’s amino acid composition. The use of compositionbased statistics is particularly beneficial for largescale automated applications of PSI-BLAST.read more
Citations
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MUSCLE: multiple sequence alignment with high accuracy and high throughput
TL;DR: MUSCLE is a new computer program for creating multiple alignments of protein sequences that includes fast distance estimation using kmer counting, progressive alignment using a new profile function the authors call the log-expectation score, and refinement using tree-dependent restricted partitioning.
Journal ArticleDOI
BLAST+: architecture and applications.
Christiam Camacho,George Coulouris,Vahram Avagyan,Ning Ma,Jason S. Papadopoulos,Kevin Bealer,Thomas L. Madden +6 more
TL;DR: The new BLAST command-line applications, compared to the current BLAST tools, demonstrate substantial speed improvements for long queries as well as chromosome length database sequences.
Journal ArticleDOI
MEGA3: Integrated software for Molecular Evolutionary Genetics Analysis and sequence alignment
TL;DR: An overview of the statistical methods, computational tools, and visual exploration modules for data input and the results obtainable in MEGA is provided.
Journal ArticleDOI
Database resources of the National Center for Biotechnology Information
David L. Wheeler,Deanna M. Church,Ron Edgar,Scott Federhen,Wolfgang Helmberg,Thomas L. Madden,Joan Pontius,Gregory D. Schuler,Lynn M. Schriml,Edwin Sequeira,Tugba O. Suzek,Tatiana Tatusova,Lukas Wagner +12 more
TL;DR: In addition to maintaining the GenBank(R) nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides data analysis and retrieval resources for the data in GenBank and other biological data made available through NCBI’s website.
Book
Accelerated Profile HMM Searches
TL;DR: An acceleration heuristic for profile HMMs, the “multiple segment Viterbi” (MSV) algorithm, which computes an optimal sum of multiple ungapped local alignment segments using a striped vector-parallel approach previously described for fast Smith/Waterman alignment.
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