Mammalian production of an isotopically enriched outer domain of the HIV-1 gp120 glycoprotein for NMR spectroscopy |
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Authors: | Mallika?Sastry Ling?Xu Ivelin?S?Georgiev Carole?A?Bewley Gary?J?Nabel Email author" target="_blank">Peter?D?KwongEmail author |
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Institution: | (1) Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 40 Convent Drive, Bethesda, MD 20892-3027, USA;(2) Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA; |
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Abstract: | NMR spectroscopic characterization of the structure or the dynamics of proteins generally requires the production of samples
isotopically enriched in 15N, 13C, or 2H. The bacterial expression systems currently in use to obtain isotopic enrichment, however, cannot produce a number of eukaryotic
proteins, especially those that require post-translational modifications such as N-linked glycosylation for proper folding
or activity. Here, we report the use of an adenovirus vector-based mammalian expression system to produce isotopically enriched
15N or 15N/13C samples of an outer domain variant of the HIV-1 gp120 envelope glycoprotein with 15 sites of N-linked glycosylation. Yields
for the 15N- and 15N/13C-labeled gp120s after affinity chromatography were 45 and 44 mg/l, respectively, with an average of over 80% isotope incorporation.
Recognition of the labeled gp120 by cognate antibodies that recognize complex epitopes showed affinities comparable to the
unlabeled protein. NMR spectra, including 1H-15N and 1H-13C HSQCs, 15N-edited NOESY-HSQC, and 3D HNCO, were of high quality, with signal-to-noise consistent with an efficient level of isotope
incorporation, and with chemical shift dispersion indicative of a well-folded protein. The exceptional protein yields, good
isotope incorporation, and ability to obtain well-folded post-translationally modified proteins make this mammalian system
attractive for the production of isotopically enriched eukaryotic proteins for NMR spectroscopy. |
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