ATP-induced conformational dynamics in the AAA+ motor unit of magnesium chelatase.

Summary, in English

Mg-chelatase catalyzes the first committed step of the chlorophyll biosynthetic pathway, the ATP-dependent insertion of Mg(2+) into protoporphyrin IX (PPIX). Here we report the reconstruction using single-particle cryo-electron microscopy of the complex between subunits BchD and BchI of Rhodobacter capsulatus Mg-chelatase in the presence of ADP, the nonhydrolyzable ATP analog AMPPNP, and ATP at 7.5 A, 14 A, and 13 A resolution, respectively. We show that the two AAA+ modules of the subunits form a unique complex of 3 dimers related by a three-fold axis. The reconstructions demonstrate substantial differences between the conformations of the complex in the presence of ATP and ADP, and suggest that the C-terminal integrin-I domains of the BchD subunits play a central role in transmitting conformational changes of BchI to BchD. Based on these data a model for the function of magnesium chelatase is proposed.

• Author: Joakim Lundqvist; Hans Elmlund; Ragna Peterson Wulff; Lisa Berglund; Dominika Elmlund; Cecilia Emanuelsson; Hans Hebert; Robert D Willows; Mats Hansson; Martin Lindahl; Salam Al-Karadaghi
• Department/s: Biochemistry and Structural Biology
• Publishing year: 2010
• Language: English
• Pages: 354-365
• Publication/Series: Structure
• Volume: 18
• Issue: 3
• Links: http://dx.doi.org/10.1016/j.str.2010.01.001
• Document type: Journal article
• Publisher: Cell Press
• Topic: Biological Sciences
• Status: Published
• ISBN/ISSN/Other: ISSN: 0969-2126