Methionine Sulfoxide Reductase B Regulates the Activity of Ascorbate Peroxidase of Banana Fruit

Abstract

Ascorbate peroxidase (APX) is a key antioxidant enzyme that is involved in diverse developmental and physiological process and stress responses by scavenging H2O2 in plants. APX itself is also subjected to multiple posttranslational modifications (PTMs). However, redox-mediated PTM of APX in plants remains poorly understood. Here, we identified and confirmed that MaAPX1 interacts with methionine sulfoxide reductase B2 (MsrB2) in bananas. Ectopic overexpression of MaAPX1 delays the detached leaf senescence induced by darkness in Arabidopsis. Sulfoxidation of MaAPX1, i.e., methionine oxidation, leads to loss of the activity, which is repaired partially by MaMsrB2. Moreover, mimicking sulfoxidation by mutating Met36 to Gln also decreases its activity in vitro and in vivo, whereas substitution of Met36 with Val36 to mimic the blocking of sulfoxidation has little effect on APX activity. Spectral analysis showed that mimicking sulfoxidation of Met36 hinders the formation of compound I, the first intermediate between APX and H2O2. Our findings demonstrate that the redox state of methionine in MaAPX1 is critical to its activity, and MaMsrB2 can regulate the redox state and activity of MaAPX1. Our results revealed a novel post-translational redox modification of APX.

Atomically Dispersed Cu Nanozyme with Intensive Ascorbate Peroxidase Mimic Activity Capable of Alleviating ROS‐Mediated Oxidation Damage

“…[ 1 , 2 ] Among the antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase which mainly occur in peroxisomes), ascorbate peroxidase (APX) with a high affinity against H 2 O 2 plays a crucial role in promoting plant cellular tolerance to oxidative stress through catalyzing the conversion of H 2 O 2 into H 2 O using ascorbic acid as electron donor. [ 3 , 4 ] Though APX functions as the vital regulator for maintaining the ROS balance in plant cells, APX is susceptible to multiple redox‐related post‐transitional modifications (PTMs) and easily inactivated by specific inhibitors through blocking the oxidation of H 2 O 2 with heme. [ 4 , 5 ] Recently much effort has been put into regulating the activities of APXs in terms of post‐transitional modifications of the proteins, [ 6 , 7 ] it only succeeded marginally.…”

“…[ 3 , 4 ] Though APX functions as the vital regulator for maintaining the ROS balance in plant cells, APX is susceptible to multiple redox‐related post‐transitional modifications (PTMs) and easily inactivated by specific inhibitors through blocking the oxidation of H 2 O 2 with heme. [ 4 , 5 ] Recently much effort has been put into regulating the activities of APXs in terms of post‐transitional modifications of the proteins, [ 6 , 7 ] it only succeeded marginally. Until now, for characterizing the regulation by PTMs, only a limited number of proteins have been investigated.…”

The redox cycling of STAT2 maintains innate immune homeostasis

“…However, the function of the reductase activity of MSRB2 in physiological processes is not well understood. Importantly, to date, only two proteins, F-actin and APX, have been proven to be substrates of MSRB2 (Bai et al, 2020;Xiao et al, 2021). Our study establishes STAT2 as another substrate of MSRB2, which provides direct evidence linking the redox system to immunity.…”

“…In this study, MSRB2 is found to positively regulate innate immunity by specifically reducing STAT2 methionine oxidation, which corresponds to the beneficial effects of antioxidants in human physiology and pathology (Forman and Zhang, 2021). Previous studies on MSRB2 have mainly focused on its role in resistance to oxidative stress, which is involved in cytokinesis, development of seeds, and mitochondrial functions (Bai et al, 2020;Stolarska et al, 2020;Xiao et al, 2021;Lee et al, 2019;Otte et al, 2014). However, the function of the reductase activity of MSRB2 in physiological processes is not well understood.…”

Methionine sulfoxide reductase B5 plays a key role in preserving seed vigor and longevity in rice (Oryza sativa)

“…Considering the mode of action of MSR, it can be speculated that MSRB5 possibly reverts age‐induced MetSO modification that occurs in various susceptible proteins, thereby sustaining their functional competence, which maintains ROS homeostasis in seeds. Previous reports indicated that the antioxidative enzyme APX undergoes sulfoxide modification which inhibits its enzyme activity in banana fruit (Jiang et al ., 2020; Xiao et al ., 2021). However, as with antioxidative enzymes, it is not known whether PIMT also undergoes undesired sulfoxide modification under oxidative environments in seeds or whether MSR repairs such damage.…”