Time-Resolved Dissociation of the Light-Harvesting 1 Complex of Rhodospirillum rubrum, Studied by Infrared Laser Temperature Jump

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• 作者：Anjali Pandit ; Hairong Ma ; Ivo H. M. van Stokkum ; Martin Gruebele ; and Rienk van Grondelle
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：December 24, 2002
• 年：2002
• 卷：41
• 期：51
• 页码：15115 - 15120
• 全文大小：66K
• 年卷期：v.41,no.51(December 24, 2002)
• ISSN：1520-4995

文摘

For the first time, data are presented on the time-resolved disassembly reaction of a highlyorganized membrane protein complex in vitro. The photosynthetic core light-harvesting complex of thebacterial strain Rhodospirillum rubrum G9 consists of 12-16 dimeric subunits that in vivo are associatedwith the photosynthetic reaction center in a ringlike manner. Isolated in a detergent solution, its appearanceeither as a ringlike complex (called B873 and absorbing at 873 nm), subunit dimer (called B820 andabsorbing at 820 nm), or monomeric form (called B777 and absorbing at 777 nm) is strongly temperature-dependent. In thermodynamic equilibria between B820 and B873, intermediate-sized complexes havealso been observed that have absorption maxima around 850 nm. It is unknown whether these structuresappear as intermediates in the kinetic B820-B873 (dis)assembly reaction. In this paper disassembly ofthe light-harvesting complex into its dimeric subunits was followed spectroscopically on a time scale upto 200 ms, upon applying an infrared laser-induced temperature jump. The full dissociation process appearsto take place on a time scale of tens to hundreds of milliseconds, the rates becoming faster at higherstarting temperatures. Applying the same technique, the dissociation reaction of dimeric subunits intomonomers also could be established. This dissociation process occurred on a much faster time scale andtook place within the 500 s response time of our detection system.