Nanomechanical and Thermophoretic Analyses of the Nucleotide-Dependent Interactions between the AAA(+) Subunits of Magnesium Chelatase.

ABSTRACT: In chlorophyll biosynthesis, the magnesium chelatase enzyme complex catalyzes the insertion of a Mg(2+) ion into protoporphyrin IX. Prior to this event, two of the three subunits, the AAA(+) proteins ChlI and ChlD, form a ChlID-MgATP complex. We used microscale thermophoresis to directly determine dissociation constants for the I-D subunits from Synechocystis, and to show that the formation of a ChlID-MgADP complex, mediated by the arginine finger and the sensor II domain on ChlD, is necessary for the assembly of the catalytically active ChlHID-MgATP complex. The N-terminal AAA(+) domain of ChlD is essential for complex formation, but some stability is preserved in the absence of the C-terminal integrin domain of ChlD, particularly if the intervening polyproline linker region is retained.

SUBMITTER: Adams NB 

PROVIDER: S-EPMC4882731 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature