Crystallization and preliminary x-ray investigation of recombinant human granulocyte-macrophage colony-stimulating factor

Molecular structure of human GM-CSF in complex with a disease-associated anti-human GM-CSF autoantibody and its potential biological implications

Polyclonal autoantibodies against human GM-CSF (granulocyte/macrophage colony-stimulating factor) are a hallmark of PAP (pulmonary alveolar proteinosis) and several other reported autoimmune diseases. MB007 is a high-affinity anti-(human GM-CSF) autoantibody isolated from a patient suffering from PAP which shows only modest neutralization of GM-CSF bioactivity. We describe the first crystal structure of a cytokine-directed human IgG1λ autoantibody-binding fragment (Fab) at 1.9 Å (1 Å=0.1 nm) resolution. Its CDR3-H substantially differs from all VH7 germline IgG1 structures reported previously. We derive a reliable model of the antigen-autoantibody complex by using NMR chemical shift perturbation data in combination with computational methods. Superposition of the modelled complex structure with the human GM-CSF-GM-CSF ternary receptor complex reveals only little overlap between receptor and Fab when bound to GM-CSF. Our model provides a structural basis for understanding the mode of action of the MB007 autoantibody.

CD and fluorescence studies of the human granulocyte-macrophage colony-stimulating factor and related peptide conformations in aqueous solution

The absorption, CD, and fluorescence emission spectra, and the fluorescence emission and depolarization lifetimes of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) and related peptides previously tested for their immunological activity, were measured in water at various pHs and temperatures to obtain information on their conformation in solution. The aim was to correlate the amino acid sequences, and the chain conformations and dynamics of the peptides, with their immunological properties. The CD spectrum of hGM-CSF revealed, as expected, a structure in solution similar to that in the crystalline state, but the fluorescence data suggest that the Trp 122 residue is more accessible to the solvent than the x-ray data would lead one to expect. They also suggest that some flexibility exists between the protein's two domains, one made up of the alpha-helices A and C and the other of the alpha-helices B and D plus the two beta-strands. In aqueous solution, none of the tested peptide CD spectra could be linked to a recognizable ordered conformation, i.e., an alpha-helix or a beta-sheet. The fluorescence of the peptide 11-24 suggests that the Trp 13 residue may appear in two types of situations: (a) in aqueous solution and (b) within a globular structure. Its CD spectra show that the tryptophan residue exists in both cases in a highly asymmetric environment independent of the pH.

Three-dimensional structure of recombinant human granulocyte-macrophage colony-stimulating factor

The crystal structure of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) has been determined at 2.8 A resolution using multiple isomorphous replacement techniques. There are two molecules in the crystallographic asymmetric unit, which are related by an approximate non-crystallographic 2-fold axis. The overall structure is highly compact and globular with a predominantly hydrophobic core. The main structural feature of rhGM-CSF is a four alpha-helix bundle, which represents approximately 42% of the structure. The helices are arranged in a left-handed antiparallel bundle with two overhand connections. Within the connections is a two-stranded antiparallel beta-sheet. The tertiary structure of rhGM-CSF has a topology similar to that of porcine growth factor and interferon-beta. Most of the proposed critical regions for receptor binding are located on a continuous surface at one end of the molecule that includes the C terminus.

Structure-function relationships of the hematopoietic growth factors

The hematopoietic growth factors are a family of glycoproteins involved in the production of blood cells from their bone marrow precursors and in the activation of mature blood cells. Much has been learned about the structural features of these molecules responsible for their characteristic biological activities. Most studies have been based upon mutagenesis strategies of intact polypeptides and on epitope mapping of informative monoclonal antibodies to the growth factors. A more limited amount of physical data is available. This review will summarize these findings, highlight the growing body of evidence suggesting that many of these proteins share common evolutionary origins and structural elements, and hopefully point to the directions being taken for further investigations of these scientifically informative and clinically useful group of proteins.

Low-resolution structure of recombinant human granulocyte-macrophage colony stimulating factor

A recombinant form of human granulocyte-macrophage colony stimulating factor (GM-CSF) which contains no carbohydrate has been crystallized. Multiple isomorphous replacement analysis using five heavy-atom derivatives has yielded an image of the structure at 6 A resolution that showed two molecules per asymmetric unit and allowed determination of the non-crystallographic symmetry transformation. The 6 A resolution result shows that the core of GM-CSF consists of four helices. The angles at which the helices pack together distinguishes this structure from known antiparallel four-helix bundle proteins. Consideration of the amino acid sequence properties and previous structural characterizations of GM-CSF leads to an assignment of the probable protein segments that form the helices.