1dz7
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(New page: 200px<br /> <applet load="1dz7" size="450" color="white" frame="true" align="right" spinBox="true" caption="1dz7" /> '''SOLUTION STRUCTURE OF THE A-SUBUNIT OF HUMA...)
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Revision as of 14:31, 12 November 2007
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SOLUTION STRUCTURE OF THE A-SUBUNIT OF HUMAN CHORIONIC GONADOTROPIN [MODELED WITHOUT CARBOHYDRATE RESIDUES]
Overview
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.
About this Structure
1DZ7 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Solution structure of the alpha-subunit of human chorionic gonadotropin., Erbel PJ, Karimi-Nejad Y, De Beer T, Boelens R, Kamerling JP, Vliegenthart JF, Eur J Biochem. 1999 Mar;260(2):490-8. PMID:10095786
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