Sequence alignment between 3efx(D) and UniProt seq P01556 (CHTB_VIBCH):

P01556 (CHTB_VIBCH): Cholera enterotoxin subunit B from Vibrio cholerae serotype O1 (strain ATCC 39315 / El Tor Inaba N16961)
                 10        20        30        40        50        60        70        80        90       100       110       120    
         ---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+----
UniProt: MIKLKFGVFFTVLLSSAYAHGTPQNITDLCAEYHNTQIYTLNDKIFSYTESLAGKREMAIITFKNGAIFQVEVPGSQHIDSQKKAIERMKDTLRIAYLTEAKVEKLCVWNNKTPHAIAAISMAN
         .....................X.....X..X.........X....X.....................X.......XXXXXX.................................XX........
PDB seq: ---------------------APQNITELCSEYHNTQIYTINDKILSYTESLAGKREMAIITFKNGATFQVEVPG------QKKAIERMKDTLRIAYLTEAKVEKLCVWNNKTPNSIAAISMA-
                              ---------+---------+---------+---------+---------+----      ---------+---------+---------+---------+-- 
                                      10        20        30        40        50                  70        80        90       100