Novel insights into enzymatic systems controlling GSNO homeostasis and GSNO-based redox modifications in plants

S-nitrosylation is a redox post-translational modification widely recognized to play an important role in cellular signaling as it can modulate protein function and conformation. At the physiological level, nitrosoglutathione (GSNO) is considered the major physiological NO-releasing compound due to its ability to transfer the NO moiety to protein thiols. However, the enzymatic systems controlling its intracellular concentration as well as the structural determinants regulating its redox specificity are not fully elucidated. Here we provide novel insights into a new class of enzymes belonging to the aldo-keto reductase (AKR) protein superfamily which may be integrated with NADH-dependent GSNO reductase (GSNOR) activity to control NO homeostasis in plants. The molecular mechanisms underlying GSNO-dependent thiol oxidation were investigated using plant glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a model protein tool. Starting from the 3D structure, we carried out comput!
ational studies to identify the protein residues involved in GSNO binding and to disclose the reaction mechanism of GSNO-dependent trans-nitrosylation. Based on our findings, we provide functional and structural insights into the control of GSNO homeostasis in plant cells and into the regulatory mechanisms mediated by GSNO.