I recently faced a problem that seemed trivial to solve at first but (as always) was not: How to get the taxonomic distribution of proteins with a given interpro domain?

I start off even without knowing exactly which protein domains to look at (I wanted to look at all that were present in certain proteins). To do this, I query Uniprot through biomart to get all the annotated interpro domains present in a group of proteins. I also get a bunch of other info (other IDs, names) along.

import pandas as pd
from biomart import BiomartServer, BiomartDataset

ids = ["P01106", "P17947"] # some examples

# connect to biomart
server = BiomartServer("http://www.biomart.org/biomart")
uniprot = server.datasets['uniprot']

# query interpro domains for the prots
attributes = ['accession', 'ensembl_id', 'entry_type', 'gene_name', 'name', 'interpro_id']
response = uniprot.search({
'filters': {'accession': ids},
'attributes': attributes
})

# put in dataframe
df = pd.DataFrame([line.split("\t") for line in list(response.content.strip().split("\n"))],
columns=attributes
)

We now switch to the Interpro database and get the scientific name (and other stuff) of species with proteins containing these interpro domains. Again Biomart is our friend.

domains = df['interpro_id']
attributes = ['entry_id', 'entry_type', 'entry_name', 'taxonomy_scientific_name']

interpro = BiomartDataset("http://www.biomart.org/biomart", name='entry')

for domain in domains:
# Query taxonomies with domains
response = interpro.search({
'filters': {'entry_id': domain},
'attributes': attributes
})
taxons = pd.DataFrame([line.split("\t") for line in list(response.content.strip().split("\n"))],
columns=attributes
)

if domain == domains[0]:
df = taxons
else:
df = pd.concat([df, taxons])

To assess the distribution of these proteins across clades of species, one needs more information about these species. Getting there was the bit not so obvious to me.

NCBI taxonomy has this type of information, but I wasn’t familiar with their APIs or services so called NCBI eutils. Luckyly there’s a Python solution for accessing NCBI’s Entrez databases thourough BioPython.

We define two functions: to get the ID of a taxon based on its name (this actually may fail if species names have appended stuff like “strain”) and to get the record (which contains a full lineage description) for that taxon based on its ID.

from Bio import Entrez

def get_tax_id(specie):
"""Get taxon ID for specie."""
specie = specie.replace(" ", "+").strip()
search = Entrez.esearch(term=specie, db="taxonomy", retmode="xml")
record = Entrez.read(search)
if int(record["Count"]) == 0:
return None
if "IdList" in record.keys():
return record['IdList'][0]


def get_tax_data(taxid):
"""Fetch the record of a taxon ID."""
search = Entrez.efetch(id=taxid, db="taxonomy", retmode="xml")
return Entrez.read(search)

Entrez.email = "" # enter your email here

# initialize empty column for taxonomy
df['taxonomy'] = None
for specie in unique(df["taxonomy_scientific_name"]):
taxid = get_tax_id(specie)
if taxid is None:
continue
data = get_tax_data(taxid)
if len(data) >= 1:
if "Lineage" in data[0].keys():
# add taxonomy to all rows with this specie name
df['taxonomy'][df['taxonomy_scientific_name'] == specie] = data[0]["Lineage"]

Full example:

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