DNA sequences encoding the subunit CHLD of plant magnesium chelatases, and determining the activity of plant magnesium chelatases

Abstract

The present invention relates to a nucleic acid molecule which encodes a protein with the function of a plant Mg chelatase subunit CHLD or an active fragment thereof; a protein which has the function of a plant Mg chelatase subunit CHLD or an active fragment thereof, preferably a recombinant protein; a method of determining the interaction of plant Mg chelatase subunits, in which a host cell is transformed with a DNA sequence as claimed in one or more of claims 1 to 3 and at least with one DNA sequence encoding a further subunit of Mg chelatase in such a manner that the interaction of the Mg chelatase gene products leads to a directly or indirectly, qualitatively or quantitatively measurable signal, preferably by activating a marker gene, and transgenic plants, transgenic plant cells, transgenic plant organs, transgenic plant seeds, transgenic propagation material comprising an abovementioned nucleic acid molecule.

1 - 29 . (canceled)  
     
     
         30 . A method for identifying inhibitors or activators of plant Mg chelatase comprising: 
 a) combining a recombinant protein having the function of a plant Mg chelatase subunit CHLD with the gene products of the DNA sequences encoding the Mg chelatase subunits I and H to make plant Mg chelatase;    b) measuring catalytic activity of the Mg chelatase in the absence of an additional chemical compound;    c) measuring catalytic activity of the Mg chelatase in the presence of at least one additional chemical compound; and    d) comparing the results of (b) and (c), whereby an inhibitor of Mg chelatase is identified by a decrease in the catalytic activity of (c), as compared with (b), and an activator of Mg chelatase is identified by an increase in the catalytic activity of (c), as compared with (b).    
     
     
         31 . The method according to  claim 30 , wherein the recombinant protein having the function of a plant Mg chelatase subunit CHLD comprises SEQ ID NO:2.  
     
     
         32 . The method according to  claim 30 , wherein the recombinant protein having the function of a plant Mg chelatase subunit CHLD is purified.  
     
     
         33 . The method according to  claim 30 , wherein step (a) is performed in intact cells.  
     
     
         34 . The method according to  claim 33 , wherein protein-containing extracts or Mg-chelatase-containing fractions are isolated from the intact cells after step (a) and before step (b).