The monomer-dimer equilibrium of stromal cell-derived factor-1 (CXCL 12) is altered by pH, phosphate, sulfate, and heparin. Protein Sci 2005 Apr;14(4):1071-81
Date
03/03/2005Pubmed ID
15741341Pubmed Central ID
PMC2253449DOI
10.1110/ps.041219505Scopus ID
2-s2.0-15244345079 (requires institutional sign-in at Scopus site) 155 CitationsAbstract
Chemokines, like stromal cell-derived factor-1 (SDF1/CXCL12), are small secreted proteins that signal cells to migrate. Because SDF1 and its receptor CXCR4 play important roles in embryonic development, cancer metastasis, and HIV/AIDS, this chemokine signaling system is the subject of intense study. However, it is not known whether the monomeric or dimeric structure of SDF1 is responsible for signaling in vivo. Previous structural studies portrayed the SDF1 structure as either strictly monomeric in solution or dimeric when crystallized. Here, we report two-dimensional NMR, pulsed-field gradient diffusion and fluorescence polarization measurements at various SDF1 concentrations, solution conditions, and pH. These results demonstrate that SDF1 can form a dimeric structure in solution, but only at nonacidic pH when stabilizing counterions are present. Thus, while the previous NMR structural studies were performed under acidic conditions that strongly promote the monomeric state, crystallographic studies used nonacidic buffer conditions that included divalent anions shown here to promote dimerization. This pH-sensitive aggregation behavior is explained by a dense cluster of positively charged residues at the SDF1 dimer interface that includes a histidine side chain at its center. A heparin disaccharide shifts the SDF1 monomer-dimer equilibrium in the same manner as other stabilizing anions, suggesting that glycosaminoglycan binding may be coupled to SDF1 dimerization in vivo.
Author List
Veldkamp CT, Peterson FC, Pelzek AJ, Volkman BFAuthors
Francis C. Peterson PhD Professor in the Biochemistry department at Medical College of WisconsinBrian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Chemokine CXCL12Chemokines, CXC
Dimerization
Heparin
Histidine
Hydrogen-Ion Concentration
Nuclear Magnetic Resonance, Biomolecular
Phosphates
Protons
Recombinant Proteins
Static Electricity
Sulfates
