Abstract
Nitric oxide (NO) is produced in plant cells by enzymatic and non-enzymatic mechanisms. Since proteins including iron-sulfur cluster are prone to form dinitrosyl complex through the reaction with NO, they are considered to be target molecules of NO. Ferredoxin (Fd) is an iron-sulfur protein ubiquitously found in living organisms. To date, however, there is no report on the reaction between NO and plant ferredoxin. Here we report that NO reacts with Fd(I) and Fd(III). NO generated in vitro by the chemical NO donor SNAP bleached the characteristic absorption peaks of the Fds. The reaction was suppressed by carboxy-PTIO, a NO scavenger. The Fd(III) in which Ser(46)-Thr(47) had been substituted by Gly-Gly showed much faster bleaching in the presence of NO. These results demonstrate that plant ferredoxin is a target of NO and suggest that Ser(46)-Thr(47) is important to protect Fd from NO.
