In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 85, No. 21 ( 1988-11), p. 7897-7901
Abstract:
Total chemical synthesis of analog proteins was used to examine the requirement for specific disulfide bridges for the biological activity of interleukin 3 (IL-3), a growth factor that stimulates multiple lineages of hemopoietic cells. Four structural analogs of the mature, 140 amino acid murine IL-3 molecule were synthesized in which specific cysteine residues were replaced by alanines. In a quantitative IL-3 assay, based on [3H]thymidine incorporation into factor-dependent cells, the IL-3 analog with alanines substituted for all four cysteines--i.e., [Ala17,79,80,140] IL-3--had 1/500th as much activity as the molecule synthesized according to the native sequence. The two analogs [Cys17,79,Ala80,140] IL-3 and [Cys17,140,Ala79,80]IL-3 had similarly low activity, whereas the [Cys17,80,Ala79,140] IL-3 analog had 2000-fold higher activity than these three analogs, and 3-fold higher than the molecule with the native sequence. This shows that in IL-3 a single disulfide bridge, between cysteines 17 and 80, is required for biological activity that approximates physiological levels. This disulfide probably stabilizes the tertiary structure of the protein to give a conformation that is optimal for function.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.85.21.7897
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
1988
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
