Abstract: The present invention relates to a protein having G-CSF-like activity comprising a) one or two polypeptide chains; b) a bundle of four ?-helices; and c) two or three amino acid linkers that connect contiguous bundle-forming ?-helices that are located on the same polypeptide chain, wherein each amino acid linker has a length between 2 and 20 amino acids. The invention also provides for a polynucleotide and a vector encoding the protein of the invention, host cells comprising said polynucleotide, a method for producing the protein of the invention and a pharmaceutical composition comprising the protein of the invention. The invention further relates to uses of the proteins of the invention as a research reagent and the use of the protein and/or pharmaceutical composition comprising the same as a medicament, e.g., for use in increasing stem cell production, for use in inducing hematopoiesis and/or for use in mobilizing hematopoietic stem cells.