ATP-Induced Conformational Dynamics in the AAA+ Motor Unit of Magnesium Chelatase

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

*Corresponding author for this work

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

Mg-chelatase catalyzes the first committed step of the chlorophyll biosynthetic pathway, the ATP-dependent insertion of Mg2+ 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 Å, 14 Å, and 13 Å 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.

Original languageEnglish
Pages (from-to)354-365
Number of pages12
JournalStructure
Volume18
Issue number3
DOIs
Publication statusPublished - 10 Mar 2010

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