title: Crystal structure of canine and bovine granulocyte-colony stimulating factor (G-CSF).
abstract: The crystal structures of recombinant canine and bovine granulocyte colony stimulating factor (G-CSF) have been determined by X-ray crystallography, using molecular replacement with recombinant human G-CSF as a model. G-CSF is a member of the cytokine family of glycoproteins that stimulate the differentiation and proliferation of blood cells. Human, bovine and canine G-CSF all have a molecular mass of about 19 kDa and share an amino acid sequence identity of about 80%. Two crystal forms of canine G-CSF have been solved. Form I recombinant canine G-CSF (rcG-CSFI; space group C2) contains one molecule in the asymmetric unit while form II canine G-CSF (rcG-CSFII; space group P2(1)) has two molecules in the asymmetric unit and bovine G-CSF (rbG-CSF; space group P2(1)2(1)2(1)) contains one molecule in the asymmetric unit. rcG-CSFI has been refined to an R factor of 20.7% with data to 2.3 A resolution and rcG-CSFII has been refined to an R factor of 19.3% with data to 2.2 A resolution. rbG-CSF has been refined to an R factor of 21.3% with data to 1.7 A resolution. The structure of human, canine and bovine G-CSF is an antiparallel 4-alpha-helical bundle with up-up-down-down connectivity. With the exception of one highly exposed loop (residues 66 to 74), the human, canine and bovine structures are very similar to each other. Using our series of G-CSF crystal structures we developed a function that describes the probability that a particular residue position (i) contributes to a G-CSF receptor binding site based on two principles, (1) high sequence conservation in the primary sequence of human, bovine, canine and murine G-CSF and (2) conservation of high solvent accessibility in the human, bovine and canine crystal structures. On the basis of this probability function as well as a comparison of G-CSF to the crystal structure of human growth hormone (hGH) complexed with the extracellular domain of the human growth hormone receptor (hGHbp), residues that contribute to potential G-CSF receptor binding sites are identified.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles 90024-1570.
authors.forename: B
authors.initials: B
authors.lastname: Lovejoy
authors.forename: D
authors.initials: D
authors.lastname: Cascio
authors.forename: D
authors.initials: D
authors.lastname: Eisenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D018360:Crystallography, X-Ray / Q000379:methods; D004285:Dogs; D016179:Granulocyte Colony-Stimulating Factor / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D011994:Recombinant Proteins; D016179:Granulocyte Colony-Stimulating Factor