Download MendeleyThe crystal structure of affinity-matured human growth hormone at 2 A resolution.
Ultsch, M.H., Somers, W., Kossiakoff, A.A., de Vos, A.M.(1994) J Mol Biol 236: 286-299
- PubMed: 8107110
- DOI: https://doi.org/10.1006/jmbi.1994.1135
- Primary Citation of Related Structures:
1HUW - PubMed Abstract:
A variant of human growth hormone (hGH), in which 15 mutations were introduced with phage display mutagenesis to improve receptor binding affinity by 400-fold, yielded two related crystal forms diffracting to high resolution. The structure of this variant was determined in both crystal forms, one at 2.0 A resolution and one at 2.4 A resolution, using molecular replacement with wild-type hGH taken from the receptor complex structure as a search model. Crystallographic refinement of the 2 A structure gave an R-value R-value of 18.5% for data in the resolution range 8 to 2 A. The final model consists of residues 1 to 128 and 155 to 191, with three side-chains modeled in alternative conformations, together with 77 water molecules. Comparison of the structure with wild-type hGH shows that most of the secondary structural elements are unchanged. The exception is the first turn of the third helix in the four-helix bundle core, which is unraveled in the present variant. Analysis of the two related packing environments suggests that this change is caused by crystal packing forces. A large change in the orientation of a short segment of helix found in the connection between the first two core helices is interpreted as evidence for rigid-body variability of this helical segment. Analysis of the mutations in light of the structure of the wild-type hGH/receptor complex shows that six of the mutations are buried in the hormone, whereas the remaining nine involve residues that interact with the receptor in the complex.
Organizational Affiliation:
Department of Protein Engineering Genetech, Inc, South San Francisco, CA 94080.
