Differential Ordering of the Protein Backbone and Side Chains during Protein Folding Revealed by Site-Specific Recombinant Infrared Probes

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• 作者：Sureshbabu Nagarajan ; Humeyra Taskent-Sezgin ; Dzmitry Parul ; Isaac Carrico ; Daniel P. Raleigh ; R. Brian Dyer
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：December 21, 2011
• 年：2011
• 卷：133
• 期：50
• 页码：20335-20340
• 全文大小：810K
• 年卷期：v.133,no.50(December 21, 2011)
• ISSN：1520-5126

文摘

The time scale for ordering of the polypeptide backbone relative to the side chains is a critical issue in protein folding. The interplay between ordering of the backbone and ordering of the side chains is particularly important for the formation of 尾-sheet structures, as the polypeptide chain searches for the native stabilizing cross-strand interactions. We have studied these issues in the N-terminal domain of protein L9 (NTL9), a model protein with mixed 伪/尾 structure. We have developed a general approach for introducing site-specific IR probes for the side chains (azide) and backbone (¹³C鈺?sup>18O) using recombinant protein expression. Temperature-jump time-resolved IR spectroscopy combined with site-specific labeling enables independent measurement of the respective backbone and side-chain dynamics with single residue resolution. We have found that side-chain ordering in a key region of the 尾-sheet structure occurs on a slower time scale than ordering of the backbone during the folding of NTL9, likely as a result of the transient formation of non-native side-chain interactions.