Premium
BchJ and BchM interact in a 1 : 1 ratio with the magnesium chelatase BchH subunit of Rhodobacter capsulatus
Author(s) -
Sawicki Artur,
Willows Robert D.
Publication year - 2010
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2010.07877.x
Subject(s) - rhodobacter , protoporphyrin ix , biochemistry , chemistry , magnesium , protein subunit , porphyrin , protoporphyrin , mutant , photodynamic therapy , organic chemistry , gene
Substrate channeling between the enzymatic steps in the (bacterio)chlorophyll biosynthetic pathway catalyzed by magnesium chelatase (BchI/ChlI, BchD/ChlD and BchH/ChlH subunits) and S ‐adenosyl‐ l ‐methionine:magnesium‐protoporphyrin IX O ‐methyltransferase (BchM/ChlM) has been suggested. This involves delivery of magnesium‐protoporphyrin IX from the BchH/ChlH subunit of magnesium chelatase to BchM/ChlM. Stimulation of BchM/ChlM activity by BchH/ChlH has previously been shown, and physical interaction of the two proteins has been demonstrated. In plants and cyanobacteria, there is an added layer of complexity, as Gun4 serves as a porphyrin (protoporphyrin IX and magnesium‐protoporphyrin IX) carrier, but this protein does not exist in anoxygenic photosynthetic bacteria. BchJ may play a similar role to Gun4 in Rhodobacter , as it has no currently assigned function in the established pathway. Purified recombinant Rhodobacter capsulatus BchJ and BchM were found to cause a shift in the equilibrium amount of Mg‐protoporphyrin IX formed in a magnesium chelatase assay. Analysis of this shift revealed that it was always in a 1 : 1 ratio with either of these proteins and the BchH subunit of the magnesium chelatase. The establishment of the new equilibrium was faster with BchM than with BchJ in a coupled magnesium chelatase assay. BchJ bound magnesium‐protoporphyrin IX or formed a ternary complex with BchH and magnesium‐protoporphyrin IX. These results suggest that BchJ may play a role as a general magnesium porphyrin carrier, similar to one of the roles of GUN4 in oxygenic organisms. Structured digital abstract• MINT‐7994803 : bchI (uniprotkb: P26239 ), bchD (uniprotkb: P26175 ) and bchH (uniprotkb: P26162 ) physically interact ( MI:0915 ) by cosedimentation in solution ( MI:0028 ) • MINT‐7994743 : bchJ (uniprotkb: P26169 ), bchI (uniprotkb: P26239 ), bchD (uniprotkb: P26175 ) and bchH (uniprotkb: P26162 ) physically interact ( MI:0915 ) by cosedimentation in solution ( MI:0028 ) • MINT‐7994762 : bchM (uniprotkb: P26236 ), bchH (uniprotkb: P26162 ), bchD (uniprotkb: P26175 ) and bchI (uniprotkb: P26239 ) physically interact ( MI:0915 ) by cosedimentation in solution ( MI:0028 )