1EKU

CRYSTAL STRUCTURE OF A BIOLOGICALLY ACTIVE SINGLE CHAIN MUTANT OF HUMAN IFN-GAMMA

Summary for 1EKU

• Entry DOI: 10.2210/pdb1eku/pdb
• Descriptor: Interferon gamma, SULFATE ION (3 entities in total)
• Functional Keywords: cytokine, protein engineering, interferon, immune system
• Biological source: Homo sapiens (Human); More
• Cellular location: Secreted: P01579
• Total number of polymer chains: 2
• Total formula weight: 63019.25

Authors

Landar, A.,Curry, B.,Parker, M.H.,DiGiacomo, R.,Indelicato, S.R.,Walter, M.R. (deposition date: 2000-03-09, release date: 2000-09-01, Last modification date: 2024-02-07)

Primary citation

Landar, A.,Curry, B.,Parker, M.H.,DiGiacomo, R.,Indelicato, S.R.,Nagabhushan, T.L.,Rizzi, G.,Walter, M.R.
Design, characterization, and structure of a biologically active single-chain mutant of human IFN-gamma.
J.Mol.Biol., 299:169-179, 2000

PubMed Abstract: A mutant form of human interferon-gamma (IFN-gamma SC1) that binds one IFN-gamma receptor alpha chain (IFN-gamma R alpha) has been designed and characterized. IFN-gamma SC1 was derived by linking the two peptide chains of the IFN-gamma dimer by a seven-residue linker and changing His111 in the first chain to an aspartic acid residue. Isothermal titration calorimetry shows that IFN-gamma SC1 forms a 1:1 complex with its high-affinity receptor (IFN-gamma R alpha) with an affinity of 27(+/- 9) nM. The crystal structure of IFN-gamma SC1 has been determined at 2.9 A resolution from crystals grown in 1.4 M citrate solutions at pH 7.6. Comparison of the wild-type receptor-binding domain and the Asp111-containing domain of IFN-gamma SC1 show that they are structurally equivalent but have very different electrostatic surface potentials. As a result, surface charge rather than structural changes is likely responsible for the inability of the His111-->Asp domain of to bind IFN-gamma R alpha. The AB loops of IFN-gamma SC1 adopt conformations similar to the ordered loops of IFN-gamma observed in the crystal structure of the IFN-gamma/IFN-gamma R alpha complex. Thus, IFN-gamma R alpha binding does not result in a large conformational change in the AB loop as previously suggested. The structure also reveals the final six C-terminal amino acid residues of IFN-gamma SC1 (residues 253-258) that have not been observed in any other reported IFN-gamma structures. Despite binding to only one IFN-gamma R alpha, IFN-gamma SC1 is biologically active in cell proliferation, MHC class I induction, and anti-viral assays. This suggests that one domain of IFN-gamma is sufficient to recruit IFN-gamma R alpha and IFN-gamma R beta into a complex competent for eliciting biological activity. The current data are consistent with the main role of the IFN-gamma dimer being to decrease the dissociation constant of IFN-gamma for its cellular receptors.

PubMed: 10860730
DOI: 10.1006/jmbi.2000.3734

Experimental method

X-RAY DIFFRACTION (2.9 Å)