Wrong protein sequence fetched with R's Biostrings readDNAStringSet function
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fastabest • 0
@fastabest-12193
Last seen 4.7 years ago

​There is somthing wrong with R package Biostrings function readDNAStringSet​. I am trying to read protein fasta sequence using this function

​fasta file http://mendel.imp.ac.at/PhyloDome/fastas.html

​library("Biostrings")

fa=readDNAStringSet("protein.fasta")​

head(fa,1)​

​    width seq                                                                                                names               
[1]   290 MRHAHTRCSRTSVAVMVSAHSCGGRGGRHRARNYVKTNSYTNSASGGV...AVNSSAHWGAMRSTAWAKHSSKVVSSANGHWYANAYKVKDYVSWRHD DROME_HH_Q02936

See the fetched fasta values and original fasta values DROME_HH_Q02936​

MRHIAHTQRCLSRLTSLVALLLIVLPMVFSPAHSCGPGRGLGRHRARNLY

​The sequence are different?

​Am I missing something

biostrings fasta protein • 1.0k views
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@martin-morgan-1513
Last seen 10 weeks ago
United States

It's a protein sequence, so use `readAAStringSet()`.

> Biostrings::readAAStringSet("tmp.fa")
  A AAStringSet instance of length 1
    width seq                                               names               
[1]   422 MRHIAHTPRGSCFMALLLLLLLA...LHWYANALYKVKDYVLPKSWRHD HH_DROHY_P56674

When read as DNAStringSet, you're missing the warning about invalid one-letter sequence codes

> Biostrings::readDNAStringSet("tmp.fa")
  A DNAStringSet instance of length 1
    width seq                                               names               
[1]   288 MRHAHTRGSCMAANRHAHSCGGR...TANGHWYANAYKVKDYVKSWRHD HH_DROHY_P56674
Warning message:
In .Call2("fasta_index", filexp_list, nrec, skip, seek.first.rec,  :
  reading FASTA file tmp.fa: ignored 134 invalid one-letter sequence codes

 

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Thank you sir it worked

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