Tetrameric assembly of hGBP1 is crucial for both stimulated GMP formation and antiviral activity

Pandita, Esha and Rajan, Sudeepa and Rahman, Safikur and Mullick, Ranajoy and Das, Saumitra and Sau, Apurba Kumar (2016) Tetrameric assembly of hGBP1 is crucial for both stimulated GMP formation and antiviral activity. In: BIOCHEMICAL JOURNAL, 473 (12). pp. 1745-1757.

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Abstract

Interferon-gamma inducible human guanylate binding protein-1 (hGBP1) shows a unique characteristic that hydrolyses GTP to a mixture of GDP and GMP through successive cleavages, with GMP being the major product. Like other large GTPases, hGBP1 undergoes oligomerization upon substrate hydrolysis, which is essential for the stimulation of activity. It also exhibits antiviral activity against many viruses including hepatitis C. However, which oligomeric form is responsible for the stimulated activity leading to enhanced GMP formation and its influence on antiviral activity, are not properly understood. Using mutant and truncated proteins, our data indicate that transition-state-induced tetramerization is associated with higher rate of GMP formation. This is supported by chimaeras that are defective in both tetramerization and enhanced GMP formation. Unlike wild-type protein, chimaeras did not show allosteric interactions, indicating that tetramerization and enhanced GMP formation are allosterically coupled. Hence, we propose that after the cleavage of the first phosphoanhydride bond GDP.P-i-bound protein dimers transiently associate to form a tetramer that acts as an allosteric switch for higher rate of GMP formation. Biochemical and biophysical studies reveal that sequential conformational changes and interdomain communications regulate tetramer formation via dimer. Our studies also show that overexpression of the mutants, defective in tetramer formation in Rep2a cells do not inhibit proliferation of hepatitis C virus, indicating critical role of a tetramer in the antiviral activity. Thus, the present study not only highlights the importance of hGBP1 tetramer in stimulated GMP formation, but also demonstrates its role in the antiviral activity against hepatitis C virus.

Item Type:	Journal Article
Publication:	BIOCHEMICAL JOURNAL
Publisher:	PORTLAND PRESS LTD
Additional Information:	Copy right of this article belongs to the PORTLAND PRESS LTD, CHARLES DARWIN HOUSE, 12 ROGER STREET, LONDON WC1N 2JU, ENGLAND
Keywords:	conformational changes; fluorescence; human guanylate binding protein; regulation of GTP hydrolysis
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	19 Jul 2016 09:48
Last Modified:	19 Jul 2016 09:48
URI:	http://eprints.iisc.ac.in/id/eprint/54186

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