Distinguishing Loss of Structure from Subunit Dissociation for Protein Complexes with Variable Temperature Ion Mobility Mass Spectrometry

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• 作者：Kamila J. Pacholarz ; Perdita E. Barran
• 刊名：Analytical Chemistry
• 出版年：2015
• 出版时间：June 16, 2015
• 年：2015
• 卷：87
• 期：12
• 页码：6271-6279
• 全文大小：387K
• ISSN：1520-6882

文摘

The thermal stability and strength of interactions in proteins are commonly measured using isothermal calorimetry and differential scanning calorimetry providing a measurement that averages over structural transitions that occur as the proteins melt and dissociate. Here, we apply variable temperature ion mobility mass spectrometry (VT-IM-MS) to study the effect of temperature on the stability and structure of four multimeric protein complexes. VT-IM-MS is used here to investigate the change in the conformation of model proteins, namely, transthyretin (TTR), avidin, concanavalin A (conA), and human serum amyloid P component (SAP) at elevated temperatures prior, during, and after dissociation up to 550 K. As the temperature of the buffer gas is increased from 300 to 350 K, a small decrease in the collision cross sections (^DTCCS_He) of protein complexes from the values at room temperature is observed, and is associated with complex compaction occurring close to the reported solution T_m. At significantly higher temperatures, each protein complex undergoes an increase in ^DTCCS_He and in the width of arrival time distributions (ATD), which is attributed to extensive protein unfolding, prior to ejection of a highly charged monomer species. This approach allows us to decouple the distinct gas phase melting temperature (T_m) from the temperature at which we see subunit dissociation. The thermally induced dissociation (TID) mechanism is observed to initially proceed via the so-called 鈥渢ypical鈥?(CID) dissociation route. Interestingly, data collected at higher analysis temperature suggests that the TID process might be adapting more 鈥渁typical鈥?dissociation route.