[PyMOL] can we add mutations to existed crystal structure models?

hi, everyone, I want to make an image to show some structual differences between wild-tye ribosomal protein S12 and mutant type in bacteria. Does anybody know how to substitute wt aa residue with mutant type in an published crystal structed? or it is a mission impossible using PyMol. Thanks a lot!
 
best regards,
 
wangPh.DMicrobial Function LabNational Food Research InstituteTsukuba, 305-8642, JAPANTel: 81-29-838-8124
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