Human interleukin-3 contains a discontinuous zinc binding domain.
The primary structure of human interleukin-3 contains two amino acid consensus sequences at Glutamate 22- Histidine 26 and Histidine 95-Histidine 98, that are characteristic for zinc binding proteins. Therefore, the hypothesis was tested that human interleukin-3 binds zinc specifically by either one or both sequences. Protein dotblotting, followed by probing with radioactive zinc demonstrated specific zinc binding of interleukin-3. Metal specificity was confirmed by competition experiments with 12 other divalent- and trivalent metal ions. Protease treatment combined with plasma desorption mass spectrometry was used to localize the zinc binding domain. Specific zinc binding was restricted to a fragment composed of Threonine 11-Lysine 28 and Asparagine 80-Lysine 100. It was found to decrease by a factor of five when either of these two amino acid stretches was missing. It is concluded that human interleukin-3 is a zinc binding protein. Interleukin-3 zinc binding capacity is largely determined by both moieties of the protein that contain the consensus sequences. In addition we propose that the zinc binding of hIL-3 is involved in (de)phosphorylation of the hIL-3 receptor.
Smit
V
V
TNO Institute of Applied Radiobiology and Immunology, Rijswijk, The Netherlands.
van Veelen
P A
PA
Tjaden
U R
UR
van der Greef
J
J
Haaijman
J J
JJ
D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002268:Carboxypeptidases / Q000378:metabolism; D002412:Cations; D006801:Humans; D007377:Interleukin-3 / Q000737:chemistry*; D013058:Mass Spectrometry; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*; D015037:Zinc Radioisotopes / Q000378:metabolism
D002412:Cations; D007377:Interleukin-3; D008670:Metals; D010446:Peptide Fragments; D015037:Zinc Radioisotopes; D002268:Carboxypeptidases; D015032:Zinc