library(pureseqtmr)
library(testthat)
library(knitr)pureseqtmr is a package to call PureseqTM from R. PureseqTM predicts the topology of a membrane protein, where the topology can be either inside, or not inside the membrane.
To be able to call PureseqTM, it needs to be installed:
pureseqtmr::install_pureseqtm()
Note that this code is not actually run, to comply with CRAN guidelines.
PureseqTM supplies some example files. Use get_example_filenames to get the path to all these files:
if (is_pureseqtm_installed()) {
get_example_filenames()
}In this example, 1bhaA.fasta will be used. To obtain the full path, use get_example_filename. get_example_filename will give an error if the file is not found.
if (is_pureseqtm_installed()) {
fasta_filename <- get_example_filename("1bhaA.fasta")
head(readLines(fasta_filename))
}Getting the topology of this protein:
if (is_pureseqtm_installed()) {
topology <- predict_topology(fasta_filename)
kable(topology)
}Or show the topology as a plot:
if (is_pureseqtm_installed()) {
plot_topology(topology)
}One needs the exact same code for a full proteome. Here we use a pureseqtmr example file, which is the COVID-19 reference proteome, as downloaded from https://www.uniprot.org/proteomes/UP000464024.
fasta_filename <- system.file(
"extdata",
"UP000464024.fasta",
package = "pureseqtmr"
)
expect_true(file.exists(fasta_filename))Show the (top of the) proteome:
head(readLines(fasta_filename))
#> [1] ">sp|P0DTC7|NS7A_SARS2 Protein 7a OS=Severe acute respiratory syndrome coronavirus 2 OX=2697049 GN=7a PE=3 SV=1"
#> [2] "MKIILFLALITLATCELYHYQECVRGTTVLLKEPCSSGTYEGNSPFHPLADNKFALTCFS"
#> [3] "TQFAFACPDGVKHVYQLRARSVSPKLFIRQEEVQELYSPIFLIVAAIVFITLCFTLKRKT"
#> [4] "E"
#> [5] ">sp|P0DTD1|R1AB_SARS2 Replicase polyprotein 1ab OS=Severe acute respiratory syndrome coronavirus 2 OX=2697049 GN=rep PE=1 SV=1"
#> [6] "MESLVPGFNEKTHVQLSLPVLQVRDVLVRGFGDSVEEVLSEARQHLKDGTCGLVEVEKGV"Getting the topology of this protein:
if (is_pureseqtm_installed()) {
topology <- predict_topology(fasta_filename)
}Instead of directly showing the raw data, the protein names are shortened first:
if (is_pureseqtm_installed()) {
topology$name <- stringr::str_match(
string = topology$name,
pattern = "..\\|.*\\|(.*)_SARS2"
)[, 2]
}Show the topology as a plot:
if (is_pureseqtm_installed()) {
plot_topology(topology)
}And tally the number of transmembrane helices per protein:
if (is_pureseqtm_installed()) {
kable(tally_tmhs(topology))
}