ABSTRACT
We have determined the structure of murine leukemia inhibitory factor (LIF) by X-ray crystallography at 2.0 A resolution. The current crystal structure comprises native LIF residues 9 to 180 with 40 ordered water molecules. For this model the R value (with a bulk solvent correction) is 18.6% on all data from 20.0 A to 2.0 A with stereochemistry typified by root mean square deviations from ideal bond lengths of 0.015 A. The mainchain fold conforms to the four alpha-helix bundle topology previously observed for several members of the hematopoietic cytokine family. Of these, LIF shows closest structural homology to granulocyte colony stimulating factor and growth hormone. Sequence alignments for the functionally related molecules oncostatin M and ciliary neurotrophic factor, when mapped to the LIF structure, indicate regions of conserved structural and surface character. Analysis of published mutagenesis data implicate two regions of receptor interaction which are located in the fourth helix and the preceding loop. A model for receptor binding based on the structure of the growth hormone ligand/receptor complex requires additional, novel features to account for these data.
Subject(s)
Antigens, CD , Interleukin-6 , Lymphokines/ultrastructure , Amino Acid Sequence , Animals , Crystallography, X-Ray , Cytokine Receptor gp130 , Growth Inhibitors/chemistry , Growth Inhibitors/metabolism , Humans , Leukemia Inhibitory Factor , Leukemia Inhibitory Factor Receptor alpha Subunit , Lymphokines/chemistry , Lymphokines/metabolism , Macromolecular Substances , Membrane Glycoproteins/metabolism , Mice , Molecular Sequence Data , Protein Structure, Tertiary , Receptors, Cytokine/metabolism , Receptors, OSM-LIF , Recombinant Fusion Proteins , Sequence Alignment , Sequence Homology, Amino Acid , Structure-Activity RelationshipABSTRACT
The structure of murine leukemia inhibitory factor (LIF) has been determined by X-ray crystallography at 2.0 A resolution. The main chain fold conforms to the four alpha-helix bundle topology previously observed for several members of the hematopoietic cytokine family. Of these, LIF shows closest structural homology to granulocyte colony-stimulating factor and growth hormone (GH). Sequence alignments for the functionally related molecules oncostatin M and ciliary neurotrophic factor, when mapped to the LIF structure, indicate regions of conserved surface character. Analysis of the biological function and receptor specificity of a series of human-mouse LIF chimeras implicate two regions of receptor interaction that are located in the fourth helix and the preceding loop. A model for receptor binding based on the structure of the GH ligand-receptor complex requires additional, novel features to account for these data.
