Sequence alignment between 4x6d(B) and UniProt seq P61769 (B2MG_HUMAN):

P61769 (B2MG_HUMAN): Beta-2-microglobulin from Homo sapiens
                 10        20        30        40        50        60        70        80        90       100       110         
         ---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------
UniProt: MSRSVALAVLALLSLSGLEAIQRTPKIQVYSRHPAENGKSNFLNCYVSGFHPSDIEVDLLKNGERIEKVEHSDLSFSKDWSFYLLYYTEFTPTEKDEYACRVNHVTLSQPKIVKWDRDM
         ..........................................................XXXXXXXXX....................................................
PDB seq: --------------------IQRTPKIQVYSRHPAENGKSNFLNCYVSGFHPSDIEVD---------KVEHSDLSFSKDWSFYLLYYTEFTPTEKDEYACRVNHVTLSQPKIVKW----
                             ---------+---------+---------+--------         --+---------+---------+---------+---------+-----    
                                     10        20        30                  50        60        70        80        90