Tyr-nitration in maize CDKA;1 results in lower affinity for ATP binding

Area of Science:

• Plant molecular biology
• Cell cycle regulation
• Abiotic stress response

Background:

• Cyclin-dependent kinase A (CDKA) is crucial for cell cycle progression, influenced by cyclin binding and phosphorylation.
• Abiotic stress induces reactive oxygen and nitrogen species (ROS/RNS), leading to cell cycle arrest and growth impairment.
• Post-translational modifications (PTMs) of key proteins like CDKA;1 are implicated in stress responses.

Purpose of the Study:

• To investigate if CDKA;1 is a target for reactive nitrogen species (RNS) in maize embryo axes under nitrosative stress.
• To determine the specific sites and functional consequences of CDKA;1 nitration.

Main Methods:

• Maize embryo axes treated with sodium nitroprusside (SNP) to induce nitrosative conditions.
• In silico analysis using GPS-YNO2 and in vitro mass spectrometry to identify nitration sites on CDKA;1.
• Spectrofluorometric assays to assess the effect of nitration on ZmCDKA;1's ATP binding affinity.

Main Results:

• Significant protein nitration of CDKA;1 was detected in maize embryo axes.
• Tyrosine residues at positions 15 and 19 (Tyr15, Tyr19) within the ATP-binding site were identified as selective nitration targets.
• Nitration reduced the affinity of ZmCDKA;1 for ATP, indicating altered kinase activity.

Conclusions:

• Tyrosine nitration of CDKA;1 occurs under nitrosative stress conditions.
• Nitration of specific tyrosine residues in the ATP-binding site modulates ZmCDKA;1 activity.
• This Tyr-nitration mechanism may actively regulate cell cycle progression during plant redox stress.