Mechanism of light modulation: identification of potential redox-sensitive cysteines distal to catalytic site in light-activated chloroplast enzymes.
Light-dependent reduction of target disulfides on certain chloroplast enzymes results in a change in activity. We have modeled the tertiary structure of four of these enzymes, namely NADP-linked glyceraldehyde-3-P dehydrogenase, NADP-linked malate dehydrogenase, sedoheptulose bisphosphatase, and fructose bisphosphatase. Models are based on x-ray crystal structures from non-plant species. Each of these enzymes consists of two domains connected by a hinge. Modeling suggests that oxidation of two crucial cysteines to cystine would restrict motion around the hinge in the two dehydrogenases and influence the conformation of the active site. The cysteine residues in the two phosphatases are located in a region known to be sensitive to allosteric modifiers and to be involved in mediating structural changes in mammalian and microbial fructose bisphosphatases. Apparently, the same region is involved in covalent modification of phosphatase activity in the chloroplast.
Li
D
D
Department of Biological Sciences, University of Illinois at Chicago 60607-7060.
Stevens
F J
FJ
Schiffer
M
M
Anderson
L E
LE
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002736:Chloroplasts / Q000201:enzymology*; D003545:Cysteine; D004220:Disulfides / Q000528:radiation effects; D007887:Fabaceae / Q000201:enzymology; D006597:Fructose-Bisphosphatase / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D008291:Malate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009249:NADP / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D010946:Plants, Medicinal; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013552:Swine; D014908:Triticum / Q000201:enzymology
D004220:Disulfides; D009249:NADP; D008291:Malate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D006597:Fructose-Bisphosphatase; D010744:Phosphoric Monoester Hydrolases; C022627:sedoheptulose-bisphosphatase; D003545:Cysteine