Sequence alignment between 1yk4(A) and UniProt seq Q9V099 (RUBR_PYRAB):

Q9V099 (RUBR_PYRAB): Rubredoxin from Pyrococcus abyssi (strain GE5 / Orsay) 
                 10        20        30        40        50   
         ---------+---------+---------+---------+---------+---
UniProt: MAKWRCKICGYIYDEDEGDPDNGISPGTKFEDLPDDWVCPLCGAPKSEFERIE
         ...XX................................................
PDB seq: -AKLSCKICGYIYDEDEGDPDNGISPGTKFEDLPDDWVCPLCGAPKSEFERIE
          --------+---------+---------+---------+---------+---
                 10        20        30        40        50