EPR Mapping of Interactions between Spin-Labeled Variants of Human Carbonic Anhydrase II and GroEL: Evidence for Increased Flexibility of the Hydrophobic Core by the Interaction

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• 作者：Malin Persson ; Per Hammarstr&ouml ; m ; Mikael Lindgren ; Bengt-Harald Jonsson ; Magdalena Svensson ; and Uno Carlsson
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：January 5, 1999
• 年：1999
• 卷：38
• 期：1
• 页码：432 - 441
• 全文大小：157K
• 年卷期：v.38,no.1(January 5, 1999)
• ISSN：1520-4995

文摘

Human carbonic anhydrase II (HCA II) interacts weakly with GroEL at room temperature. Tofurther investigate this interaction we used electron paramagnetic resonance (EPR) spectroscopy to studyHCA II cysteine mutants spin-labeled at selected positions. From our results it is evident that protein-protein interactions can be specifically mapped by site-directed spin-labeling and EPR measurements.HCA II needs to be unfolded to about the same extent as a GuHCl-induced molten-globule intermediateof the enzyme to interact with GroEL. The interaction with GroEL includes interactions with outer partsof the HCA II molecule, such as peripheral s/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-strands and the N-terminal domain, which have previouslybeen shown to be rather unstable. As a result of the interaction, the rigid and compact hydrophobic coreexhibits higher flexibility than in the molten globule, which is likely to facilitate rearrangements of misfoldedstructure during the folding process. The degree of binding to GroEL and accompanying inactivation ofthe enzyme depend on the stability of the HCA II variant, and nonspecific hydrophobic interactions appearto be most important in stabilizing the GroEL-substrate complex.