library(tidyverse)


# Function ----------------------------------------------------------------

convert <- function(three_aa_seq = NULL) {

  pep_dat <- structure(list(full = c(
    "Alanine", "Arginine", "Asparagine",
    "Aspartate", "Cysteine", "Glutamine", "Glutamate", "Glycine",
    "Histidine", "Isoleucine", "Leucine", "Lysine", "Methionine",
    "Phenylalanine", "Proline", "Serine", "Threonine", "Tryptophan",
    "Tyrosine", "Valine"
  ), three = c(
    "Ala", "Arg", "Asn", "Asp",
    "Cys", "Gln", "Glu", "Gly", "His", "Ile", "Leu", "Lys", "Met",
    "Phe", "Pro", "Ser", "Thr", "Trp", "Tyr", "Val"
  ), one = c(
    "A",
    "R", "N", "D", "C", "Q", "E", "G", "H", "I", "L", "K", "M", "F",
    "P", "S", "T", "W", "Y", "V"
  )), .Names = c("full", "three", "one"), class = c("tbl_df", "tbl", "data.frame"), row.names = c(
    NA,
    -20L
  ))
  str_split(three_aa_seq, pattern = "-")[[1]] %>%
    as.tibble() %>%
    rename(three = value) %>%
    inner_join(pep_dat, by = "three") %>%
    pull(one) %>%
    paste(., collapse = "")
}

tribble(
  ~ pep_name, ~ three_seq,
  "PA_19", "His-Ser-Leu-Gly-Lys-Trp-Leu-Gly-His-Pro-Asp-Lys-Phe",
  "PA_20", "Thr-Ala-Pro-Arg-Ser-Leu-Arg-Arg-Ser-Ser-Cys-Phe-Gly-Gly-Arg-Met-Asp-Arg-Ile-Gly-Ala-Gln-Ser-Gly-Leu-Gly-Cys-Asn-Ser-Phe-Arg-Tyr"
) %>%
  mutate(pep = convert(three_aa_seq = three_seq))