| Abstract: | Glutamate synthase (GOGAT) from Chlamydomonas reinhardtii is able to form functional covalent complexes with its substrate ferredoxin (Fd), either wild-type (WTFd) or recombinant form (rFd). However, when Fd carboxyl groups were chemically modified (mdFd), no complexes were detected and its ability to serve as electron donor for glutamate synthase activity was also decreased.
By site-directed mutagenesis, we have demonstrated that Fd glu91 and a negative core in the helix α1 are critical for Fd interaction
with this enzyme and its functionality as electron carrier for glutamate synthase. As a previous step to elucidate the specific
positive charged residues involved in glutamate synthase interaction with Fd, we have isolated a cDNA, CrFG-3, encoding Fd-GOGAT from C. reinhardtii. The cDNA comprised about 60% of the protein and sequence comparison showed that CrFG-3 was structurally more similar to higher plant enzymes than to the corresponding prokaryotic GOGAT. Two conserved domains
were present in this protein fragment, the FMN-binding domain and the cysteines involved in the iron–sulfur cluster binding.
This revised version was published online in June 2006 with corrections to the Cover Date. |
