1DZ7

Solution structure of the a-subunit of human chorionic gonadotropin [modeled without carbohydrate residues]

Summary for 1DZ7

• Entry DOI: 10.2210/pdb1dz7/pdb
• Related: 1HCN 1HRP 1XUL
• Descriptor: CHORIONIC GONADOTROPIN (1 entity in total)
• Functional Keywords: glycoprotein, chorionic gonadotropin, chorionic gonadotropin free a subunit, glycoprotein structure, cystine knot, xplor
• Biological source: HOMO SAPIENS (HUMAN)
• Total number of polymer chains: 1
• Total formula weight: 10217.77

Authors

Erbel, P.J.A.,Karimi-Nejad, Y.,De Beer, T.,Boelens, R.,Kamerling, J.P.,Vliegenthart, J.F.G. (deposition date: 2000-02-18, release date: 2000-02-29, Last modification date: 2024-10-23)

Primary citation

Erbel, P.J.,Karimi-Nejad, Y.,De Beer, T.,Boelens, R.,Kamerling, J.P.,Vliegenthart, J.F.
Solution structure of the alpha-subunit of human chorionic gonadotropin.
Eur.J.Biochem., 260:490-498, 1999

PubMed Abstract: The three-dimensional solution structure of the alpha-subunit in the alpha, beta heterodimeric human chorionic gonadotropin (hCG), deglycosylated with endo-beta-N-acetylglucosaminidase-B (dg-alpha hCG), was determined using 2D homonuclear and 2D heteronuclear 1H, 13C NMR spectroscopy at natural abundance in conjunction with the program package XPLOR. The distance geometry/simulated annealing protocol was modified to allow for the efficient modelling of the cystine knot motif present in alpha hCG. The protein structure was modelled with 620 interproton distance restraints and the GlcNAc residue linked to Asn78 was modelled with 30 protein-carbohydrate and 3 intraresidual NOEs. The solution structure of dg-alpha hCG is represented by an ensemble of 27 structures. In comparison to the crystal structure of the dimer, the solution structure of free dg-alpha hCG exhibits: (a) an increased structural disorder (residues 33-57); (b) a different backbone conformation near Val76 and Glu77; and (c) a larger flexibility. These differences are caused by the absence of the interactions with the beta-subunit. Consequently, in free dg-alpha hCG, compared to the intact dimer, the two hairpin loops 20-23 and 70-74 are arranged differently with respect to each other. The beta-GlcNAc(78) is tightly associated with the hydrophobic protein-core in between the beta-hairpins. This conclusion is based on the NOEs from the axial H1, H3, H5 atoms and the N-acetyl protons of beta-GlcNAc(78) to the protein-core. The hydrophobic protein-core between the beta-hairpins is thereby shielded from the solvent.

PubMed: 10095786
DOI: 10.1046/j.1432-1327.1999.00188.x

Experimental method

SOLUTION NMR