Structure and Dynamics of the Actin Filament

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• 作者：Jing-Qu Guan ; Keiji Takamoto ; Steven C. Almo ; Emil Reisler ; and Mark R. Chance
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：March 8, 2005
• 年：2005
• 卷：44
• 期：9
• 页码：3166 - 3175
• 全文大小：1072K
• 年卷期：v.44,no.9(March 8, 2005)
• ISSN：1520-4995

文摘

The structures of filamentous Mg-ATP-actin (F actin) in the presence and absence of KClhave been mapped with hydroxyl radicals (·OH) generated by synchrotron X-ray radiolysis. Proteolysisand mass spectrometry (MS) analysis revealed 52 reactive side-chain sites from 27 distinct peptides withinactin. The reactivities of these probe sites with ·OH in the F-actin states are compared with those ofMg-ATP-G-actin (monomers) analyzed previously [Guan, J.-Q. et al. (2003) Biochemistry 42, 11992-12000]. Filament-dependent protection within subdomains 2, 3, and 4 and at the C terminus is consistentwith longitudinal contacts of monomers within the filament helical structure as predicted by the Holmesmodel. In the absence of KCl, the extent of filament-dependent protection rarely reached 3-fold, consistentwith a highly dynamic filament characterized by relatively weak interactions between actin protomers.However, in the presence of KCl, the extents of protection are significantly increased, consistent with awell-ordered, more tightly packed filament structure. Filament-dependent enhancements of reactivity notpredicted by the Holmes model are seen for a peptide that overlaps the "hydrophobic plug" (H-plug)region and for a peptide that forms contacts with the polyphosphate moiety of the bound nucleotide.Overall, these data are both consistent with and complementary to a recent deuterium-exchange MS studyof filamentous actin [Chik, J. K., and Schriemer, D.C. (2003) J. Mol. Biol. 334, 373-385], which alsodid not detect any burial of the H plug upon formation of filaments.