New releases from NCBI: IgBLAST 1.7.0 and Sequence Viewer 3.21


IgBLAST 1.7.0 release

A new version of IgBLAST is now available on FTP, with the following new features:

  1. Specify whether overlapping nucleotides at VDJ junctions are allowed in matching V, D, and J genes.
  2. Set a custom J gene mismatch penalty
  3. Report the CDR3 start and stop positions in the sub-region table
  4. Use alignment length instead of percent identity as the tie-breaker for hits with identical blast scores, improving accuracy in the V, D, J gene assignment.

IgBLAST was developed at the NCBI to facilitate the analysis of immunoglobulin and T cell receptor variable domain sequences.

Continue reading

New Pandoravirus Sequences are Accessible in GenBank


In the July 19, 2013 issue of the journal Science, an interesting article describes the discovery and characterization of two “giant” viruses that are proposed to comprise the first members of the “Pandoravirus” genus.

Nadege Philippe and co-workers obtained the viruses from sediment samples in Chile and Australia and found that they have no morphological resemblance to any previously defined virus families. The investigators isolated the genomes of these viruses and sequenced them using a variety of NextGen methodologies. They then assembled the reads into contigs and characterized them using various sequence similarity algorithms (including NCBI’s BLAST and CD-Search). Interestingly, while related to each other, the genomes were not similar to those of any other organism or virus. Additionally, 93% of protein-coding sequences had no recognizable homologs.

Continue reading

Using Conserved Domains to Find Protein Homologs


If you’re a protein researcher, one thing you may want to do is to find homologs for a protein of interest on the basis of its sequence. This can provide insights into what the protein does and how it does it, and may identify proteins with known three-dimensional structures that can serve as models for the protein of interest. The Conserved Domains Database (CDD) groups proteins that have strong sequence similarity to protein domain fingerprints and allows you to search these groups with any protein sequence. Such searches are often more sensitive than standard BLAST searches since the scoring matrices used are tuned to locate important functional sites and sequence motifs that are highly conserved within the domain. You can then use the results to explore the evolutionary relationships of these proteins or identify these important sequence and structural features.

Here is a method to find protein sequences from many organisms that contain a particular conserved domain:

Continue reading