Glutamate synthase mutants

The evidence, based on the isolation of GS and glutamate synthase mutants, for the role of the glutamate synthase cycle in the photorespiratory nitrogen cycle as discussed in Section III,B,3, mitochondrial GDH-deficient mutant of Zea mays has been isolated and is being investigated by Rhodes et al. (1989). In the absence of MSO, wild-type plants have a higher shoot/root ratio and show a... 

Mutant lines of A. thaliana (Somerville and Ogren, 1983) and barley (Walls-grove et al, 1986) have been isolated and shown to have properties very similar to that of a mutant lacking glutamate synthase. By a detailed analysis of the chloroplast envelope, the specific protein missing in the 2-oxoglutarate uptake mutant of A. thaliana has been identified (Somerville and Somerville, 1985). 

An interesting mutation is replacement of alanine 62 of the c subunit with serine. This mutant will support ATP synthase using Li+ instead of H+.237 Certain alkylophilic bacteria, such as Propionigenium modestum, have an ATP synthase that utilizes the membrane potential and a flow of Na+ ions rather than protons through the c subunits.238 240c The sodium transport requires glutamate 65, which fulfills the same role as D61 in E. coli, and also Q32 and S66. Study of mutants revealed that the polar side chains of all three of these residues bind Na+, that E65 and S66 are needed to bind Li+, and that only E65 is needed for function with H+. 

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