Related Experiment Videos
Disulfide structures of human interleukin-6 are similar to those of human granulocyte colony stimulating factor
C L Clogston1, T C Boone, B C Crandall
1Amgen Inc, Thousand Oaks, California 91320.
Insights
Human interleukin-6 (IL-6) shares sequence homology with granulocyte colony-stimulating factor, forming two disulfide bonds crucial for its structure. These findings reveal structural similarities between IL-6 and G-CSF.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Human interleukin-6 (IL-6) and granulocyte colony-stimulating factor (G-CSF) are key cytokines.
- Sequence analysis reveals approximately 30% homology in the N-terminal regions of IL-6 and G-CSF.
- The relative positions of cysteine residues suggest potential structural similarities.
Purpose of the Study:
- To elucidate the specific disulfide bond formation in human interleukin-6 (IL-6).
- To compare the structural features of IL-6 with those of granulocyte colony-stimulating factor (G-CSF).
Main Methods:
- Recombinant IL-6 was labeled with tritiated iodoacetate.
- Proteolytic digestion using trypsin and subtilysin was performed.
- Isolation and characterization of resulting peptides were conducted to map disulfide bonds.
Main Results:
- Labeling experiments confirmed two intramolecular disulfide bonds in IL-6, with no free sulfhydryls detected.
- Disulfide bonds were assigned to Cys44-Cys50 and Cys73-Cys83.
- These bonds form two small loops, structurally analogous to those in G-CSF.
Conclusions:
- The precise disulfide bonding pattern in IL-6 has been determined.
- IL-6 and G-CSF exhibit significant structural similarities due to conserved disulfide bond arrangements.
- This structural similarity may imply shared functional mechanisms or evolutionary relationships.
Abstract:
The amino acid sequences of human interleukin-6 and granulocyte colony stimulating factor are approximately 30% homologous in the N-terminal region. The relative positions of four half-cystines in human interleukin-6 (IL-6) match four of the five in human granulocyte colony stimulating factor. Labeling experiments of recombinant interleukin-6 with tritiated iodoacetate confirmed that the molecule forms two intramolecular disulfide bonds and contains no detectable level of free sulfhydryls. By isolation and characterization of tryptic and subtilytic peptides obtained from different proteolytic digestions, the disulfide bonds of the IL-6 molecule were assigned to Cys44-Cys50 and Cys73-Cys83. The two disulfide bridges form two small loops which are separated by 22 amino acids. These structures are similar to those of recombinant granulocyte colony stimulating factor.