Mi. Garcia-sanchez et al., Glutamate synthase from Chlamydomonas reinhardtii: Interaction studies with its substrate ferredoxin and molecular cloning, PLANT SOIL, 221(1), 2000, pp. 59-65
Glutamate synthase (GOGAT) from Chlamydomonas reinhardtii is able to form f
unctional covalent complexes with its substrate ferredoxin (Fd), either wil
d-type ((WT)Fd) or recombinant form ((r)Fd). However, when Fd carboxyl grou
ps were chemically modified ((md)Fd), no complexes were detected and its ab
ility to serve as electron donor for glutamate synthase activity was also d
ecreased. By site-directed mutagenesis, we have demonstrated that Fd glu91
and a negative core in the helix alpha 1 are critical for Fd interaction wi
th this enzyme and its functionality as electron carrier for glutamate synt
hase. As a previous step to elucidate the specific positive charged residue
s involved in glutamate synthase interaction with Fd, we have isolated a cD
NA, CrFG-3, encoding Fd-GOGAT from C. reinhardtii. The cDNA comprised about
60% of the protein and sequence comparison showed that CrFG-3 was structur
ally more similar to higher plant enzymes than to the corresponding prokary
otic GOGAT. Two conserved domains were present in this protein fragment, th
e FMN-binding domain and the cysteines involved in the iron-sulfur cluster
binding.