Structural Transitions of Translation Initiation Factor IF2 upon GDPNP and GDP Binding in Solution

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• 作者：Louise Car酶e Vohlander Rasmussen ; Cristiano Luis Pinto Oliveira ; Jan Skov Pedersen ; Hans Uffe Sperling-Petersen ; Kim Kusk Mortensen
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：November 15, 2011
• 年：2011
• 卷：50
• 期：45
• 页码：9779-9787
• 全文大小：479K
• 年卷期：v.50,no.45(November 15, 2011)
• ISSN：1520-4995

文摘

Three protein factors ensure rapid and accurate initiation of translation in bacteria. Translation initiation factor IF2 is a ribosome-dependent GTPase, which is important for correct positioning of initiator tRNA on the 30S subunit as well as ribosomal subunit joining. The solution structure of the free C-terminal part of IF2 (IF2C, comprising domains IV to VI-2) was previously determined by small-angle X-ray scattering (SAXS) [Rasmussen, L. C., et al. (2008) Biochemistry 47, 5590鈥?598]. In this study, adding GDP or nonhydrolyzable GTP analogue GDPNP to the protein in solution caused structural changes in the protein, in agreement with recent data determined via isothermal titration calorimetry [Hauryliuk, V., et al. (2009) J. Mol. Biol. 394, 621鈥?26]. The p(r) function indicated an elongated conformation supported by radii of gyration of 40.1 and 44.9 脜 and maximum dimensions of 125 and 150 脜 for IF2C with GDPNP and GDP, respectively. The SAXS data were used to model the structure of IF2C bound to either GDPNP or GDP. The structural transitions of IF2C upon GDPNP binding and following nucleotide hydrolysis support the concept of cofactor-dependent conformational switching rather than the classical model for GTPase activity.