Crystal structure of human α-lactalbumin at 1·7 Å resolution

K. Ravi Acharya, Jingshan Ren, David I. Stuart, David C. Phillips, Roger E. Fenna

Research output: Contribution to journalArticlepeer-review


The three-dimensional X-ray structure of human α-lactalbumin, an important component of milk, has been determined at 1·7 Å (0·17 nm) resolution by the method of molecular replacement, using the refined structure of baboon α-lactalbumin as the model structure. The two proteins are known to have more than 90% amino acid sequence identity and crystallize in the same orthorhombic space group, P21212. The crystallographic refinement of the structure using the simulated annealing method, resulted in a crystallographic R-factor of 0·209 for the 11,373 observed reflections (F ≥ 2σ(F)) between 8 and 1·7 Å resolution. The model comprises 983 protein atoms, 90 solvent atoms and a bound calcium ion. In the final model, the root-mean-square deviations from ideality are 0·013 Å for covalent bond distances and 2·9° for bond angles. Superposition of the human and baboon α-lactalbumin structures yields a root-mean-square difference of 0·67 Å for the 123 structurally equivalent Cα atoms. The C terminus is flexible in the human α-lactalbumin molecule. The striking structural resemblance between α-lactalbumins and C-type lysozymes emphasizes the homologous evolutionary relationship between these two classes of proteins.

Original languageEnglish
Pages (from-to)571-581
Number of pages11
JournalJournal of Molecular Biology
Issue number2
Publication statusPublished - 20 Sept 1991


  • calcium binding
  • crystal structure
  • evolution
  • milk protein
  • α-lactalbumin

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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