The ChlD subunit links the motor and porphyrin binding subunits of magnesium chelatase.

The ChlD subunit links the motor and porphyrin binding subunits of magnesium chelatase. Biochem J. 2019 Jun 04;: Authors: Farmer DA, Brindley AA, Hitchcock A, Jackson PJ, Johnson B, Dickman MJ, Hunter CN, Reid JD, Adams NBP Abstract Magnesium chelatase initiates chlorophyll biosynthesis, catalysing the MgATP2- dependent insertion of a Mg2+ ion into protoporphyin IX. The catalytic core of this large enzyme complex consists of three subunits: Bch/ChlI, Bch/ChlD and Bch/ChlH (in bacteriochlorophyll and chlorophyll producing species respectively). The D and I subunits are members of the AAA+ (ATPases associated with various cellular activities) superfamily of enzymes, and they form a complex that binds to H, the site of metal ion insertion. In order to investigate the physical coupling between ChlID and ChlH in vivo and in vitro , ChlD was FLAG-tagged in the cyanobacterium Synechocystis sp. PCC 6803 and co-immunoprecipitation experiments showed interactions with both ChlI and ChlH. Co-production of recombinant ChlD and ChlH in Escherichia coli yielded a ChlDH. Quantitative analysis using microscale thermophoresis (MST) showed magnesium-dependent binding ( K d 331 ± 58 nM) between ChlD and H. The physical basis for a ChlD-H interaction was investigated using chemical crosslinking coupled with mass spectrometry (XL-MS), together with modifications that either truncate ChlD or modify single residues. We found that the C-terminal integrin I...
Source: The Biochemical Journal - Category: Biochemistry Authors: Tags: Biochem J Source Type: research